The Digital Photographer s Glossary

Transcription

1 The Digital Photographer s Glossary Tim Grey

2 # 18 percent gray The amount of light across the full spectrum reflected by a gray card, which is frequently used as the basis of photographic exposure using a light meter. A value of 18% gray for a gray card is the same as middle gray (or 50 percent gray) in a computer-based color system. Note, however, that many digital cameras are calibrated to treat a light reflectance of around 12 percent (rather than 18 percent) as middle gray. See also 50 percent gray and gray card. 50 percent gray A shade of gray that is halfway between black and white on a linear scale. A value of 50 percent gray in a computer-based color system is the same as the 18 percent gray of a gray card. See also 18 percent gray and gray card degrees Kelvin A color temperature that corresponds roughly to the illumination from the sun on a clear day, and the primary standard illuminant for a color-managed workflow. For example, under a standard color-managed workflow prints should be evaluated under a light source that corresponds to a color temperature of 5000 degrees Kelvin degrees Kelvin A color temperature that corresponds roughly to the illumination from the sun on an overcast day, and the primary target color temperature for monitor calibration and profiling in a colormanaged workflow. 2

3 A A/D conversion See analog-to-digital conversion. absolute colorimetric One of the four rendering intents for color management, most commonly used for simulating the output of one printer using a different printer. Colors that fall within the color gamut of the output device remain unchanged, and colors that fall outside the color gamut of the output device are shifted to the closest matching color. The white point of the source is maintained, making this rendering intent useful primarily when simulating the output of one device using a different device. action In Adobe Photoshop, a feature that enables you to record a series of steps you perform so they can be played back later for other images, enabling an automated workflow for imageprocessing. ADC An acronym for analog-to-digital conversion, sometimes presented as A/D or A to D. See also analog-to-digital conversion. additive primary colors The primary colors (red, green, and blue) for emitted light. In theory all visible colors can be reproduced using these primary colors, and combining all three colors at maximum intensity produces white light. These are the primary colors used by most digital displays, such as monitors and projectors. Adobe Flash A technology developed by Macromedia (which was later acquired by Adobe ) that enables cross-platform web browser-based application development that is generally focused on multimedia content. Adobe Flash technology is notably not supported by the ios platform used by the iphone and ipad. Adobe RGB A relatively large-gamut working space profile generally suitable for images that will be printed as well as displayed using digital devices, originally developed by Adobe. This color space is often referred to as Adobe RGB (1998) since it was released in

4 Advanced Photo System A film format that employed advanced features such as the ability to record data along with the exposures on the film, with a standard frame size of 25.1 x 16.7mm. Advanced Photo System-Classic Generally referred to as APS-C, originally the standard frame size for the Advanced Photo System at 25.1 x 16.7mm. The term now refers as well to a variety of digital camera image sensors that have a frame size that is approximately the same as the original APS-C film specification. Advanced Photo System-High Definition Generally referred to as APS-H, which was originally a larger version of the Advanced Photo System film format. APS-H featured a frame size of 30.2 x 16.7mm. Canon has more recently employed a digital image sensor in certain digital cameras that is referred to as an APS-H format and featuring a frame size of 28.7 x 19mm. Advanced Technology Attachment The newer name for the Integrated Drive Electronics interface for hard disk drive data connections, which had the notable feature of integrating the hard disk drive controller with the hard disk drive rather than on the controller card. AI Servo A continuous automatic focus mode featured on various Canon cameras, which uses advanced methods (thus artificial intelligence ) to intelligently determine how focus should be adjusted. The AI Servo and other continuous automatic focus modes are especially useful when photographing moving subjects. algorithm A formula or set of instructions used to perform calculations. For example, image-processing software makes use of algorithms to calculate pixel values when you apply an adjustment to an image. aliasing A jagged edge seen in elements of an image caused by the representation of curves or lines that are other than horizontal or vertical. This phenomenon is caused by the representation of these curves or lines using pixels that have a square (or rectangular) shape. See also anti-aliasing and jaggies. Allen key See hex key. Allen wrench See hex key. 4

5 alpha channel A component of an image that is typically used to define attributes of pixels within an image other than color values. A normal channel contains color information for each pixel (or luminance information in the case of a one-channel monochromatic image). An alpha channel is the same as this type of color-defining channel, but is used to define pixel opacity, the shape of saved selections, or other information that maps to individual pixels within the image. ambient light The overall indirect light illuminating a photographic subject. Direct light sources such as flash directly illuminating a subject would be considered direct light, whereas the general light reflecting off all surfaces to provide a more broad-based illumination source would be ambient light. Ambient light is also sometimes referred to as available light. amplification The process by which the signal strength of an electronic signal is increased. In the context of photography one of the most common examples of amplification relates to the increase in the strength of signals recorded by the image sensor, especially when a higher ISO value is selected. While this type of amplification can increase the amount of visible detail in an image photographed with a relatively dark exposure, it also leads to an increased risk of visible noise in the final image. See also ISO and noise. analog A system whereby the signals being measured or recorded are continuously variable. Light in the natural world, for example, is analog. This contrasts with digital information, where discrete values with fixed intervals are used to measure or record values. See also digital. analog-to-digital conversion The process by which analog information is converted to digital values. See also analog and digital. anti-aliasing A process by which the appearance of jagged edges in a digital image are reduced. For example, because pixels in a digital image are generally square a diagonal line will actually represent more of a stair-step pattern. Anti-aliasing creates a smoother appearance by blending pixel values along that jagged line. See also aliasing and jaggies. anti-aliasing filter A filter commonly used in conjunction with the image sensor in a digital camera to reduce the appearance of jagged edges in the digital image. While this produces what is generally considered to be a beneficial result, it also causes some loss of sharpness and detail in the captured image. Some image sensors (and thus cameras) do not include an anti-aliasing filter, in order to help ensure maximum sharpness and detail (though with a higher risk of moiré patterns. aperture The opening in a lens through which light passes in order to create a photographic exposure. 5

6 The term is generally also used to refer to the size of the aperture opening, presented as an f-stop that describes the ratio of the size of the aperture opening relative to the lens focal length. aperture priority mode A camera exposure mode where the photographer sets the desired lens aperture setting and the camera calculates the optimal shutter speed based on metering. APS An acronym for Advanced Photo System. See also Advanced Photo System. APS-C An acronym for Advanced Photo System-Classic. See also Advanced Photo System-Classic. APS-H An acronym for Advanced Photo System-High Definition. See also Advanced Photo System- High Definition. artifact In the context of a digital image, a variation in pixel values that is generally an unintended consequence of a process of altering pixel values. Examples include artifacts that are evidence of the compression applied to JPEG images, and sharpening artifacts caused by the addition of contrast to improve the perceived sharpness of an image. ASA An acronym for the American Standards Association (now the American National Standards Institute, or ANSI), which in the context of photography generally refers to the scale of film sensitivity ratings. The ASA film speed ratings were largely superseded by the ISO system in the 1980 s. See also ISO. aspect ratio The ratio of width to height. For example, a common aspect ratio in photography is 4:3, which indicates the image is four units wide by three units tall. A 1:1 aspect ratio would describe a square. The values are simplified to the smallest possible whole number in most cases in order to simplify comparisons. In the context of digital photography, aspect ratio is often used to describe the image sensor or a digital image. assign profile The process of defining a color profile that will be used to interpret the color number values in an image file so those values relate to specific colors. When you assign a profile to an image, the color numbers will not be changed, but rather the color associated with specific pixel values will change. Therefore the color appearance in the image may change based on the translation provided by the profile. Assigning a profile would generally only be done for situations where you are attempting to correct the appearance of colors to compensate for the behavior of a device. For example, you could assign a 6

7 camera profile to correct the color values in an image based on the measured behavior of the camera. ATA An acronym for Advanced Technology Attachment. See also Advanced Technology Attachment. Audio Video Interleave (AVI) A video format originally introduced by Microsoft in 1992 and commonly used by digital cameras to record video clips. automatic white balance A white balance setting on many digital cameras that causes the camera to calculate the estimated color compensation that needs to be applied to the image to render accurate colors, based on the color temperature of the light source illuminating the scene. AV mode See aperture priority mode. AVI An acronym for Audio Video Interleave. See also Audio Video Interleave. AWB See automatic white balance. 7

8 B back focus A situation where a camera and lens combination tends to focus behind the point at which focus was established. See also front focus. ball head A device that can be attached to a tripod or monopod (or other support), and to which a camera can be mounted, providing a platform where the position of the camera can be adjusted in various directions in order to fine-tune the position of the camera and lens relative to the subject. barrel distortion A type of lens distortion where horizontal or vertical lines in the scene are bent outward away from the center of the image. batch In the context of Adobe Photoshop Bayer pattern A pattern for the color arrangement of the filter array used on many digital camera image sensors, where out of every four photo sites one will be red, two will be green, and one will be blue (leading to the alternative name RGBG to represent the primary color values). This places an emphasis on the green range of the color spectrum for visible light, which is designed to mimic the behavior of the human visual system. The Bayer pattern is named after Bryce E. Bayer of Eastman Kodak, who invented this filter array pattern. bellows An expandable structure used on large format cameras, enabling the lens to be moved relative to the film plan in order to adjust the focus of the image. bicubic An interpolation algorithm that calculates the values of pixels to add during the enlargement of a digital image, in which a grid of sixteen pixels in a 4x4 pixel block are evaluated for each pixel being added within the image. The bicubic interpolation algorithm produces smoother transitions within the image compared to simpler interpolation algorithms. Variations on the bicubic algorithm include bicubic smoother aimed at producing better results for significant enlargements, and bicubic sharper which applies a degree of sharpening to improve the appearance of images that are reduced in size. See also interpolation. 8

9 bilinear An interpolation algorithm that calculates the values of pixels to add during the enlargement of a digital image, in which a grid of four pixels in a 2x2 pixel block are evaluated for each pixel being added within the image. The bilinear interpolation algorithm operates faster than the bicubic algorithm, but produces results that are not as smooth and that contain more artifacts of resizing. See also interpolation. bit A single digit in a binary number system, with two possible values that are ostensibly zero or one. The bit is the smallest unit of measure in a typical digital computer system. bit depth A representation of the total possible number of values for a pixel. One bit can have two possible values (nominally zero or one), and the bit depth represents the power to which two (the number of possible values) is raised to define the total number of possible pixel values per channel. The most common bit depths are 8-bit, with 256 possible values (two raised to the eighth power) for a single channel (black and white) image, and 16-bit, with 65,536 possible values for a single channel image. For color images the total number of possible color values would be equal to the number of possible values per channel cubed (raised to the third power), assuming an RGB image with three channels. That results in 16,777,216 possible color values for an 8-bit per channel (or 24-bit) RGB image, and 281,474,976,710,656 (over 281 trillion) possible color values for a 16-bit per channel (or 48-bit) RGB image. A higher bit depth helps ensure smooth gradations of tone and color even after strong adjustments are applied to an image, since there is more overhead in terms of available color values to work with. bitmap A format for storing information about a digital image in such a way that the individual color value for each pixel is recorded. This contrasts with a vector image, which defines the image based on curves and points rather than individual pixels. black The darkest color available for a digital image, generally described as having a brightness of 0% or RGB values of R0, G0, B0. While the concept of black seems like an absolute, in the context of a digital image the true appearance of black depends upon the device producing the image. For example, with digital projectors black often still has some luminance presented on the screen, and printers vary in how dark a black value they are able to produce, especially with certain papers. black and white A term that describes a monochromatic image, where all detail within the image is formed from black, white, and shades of gray. See also monochrome. 9

10 black point compensation An option available when translating color values in an image from one color profile to another where the value of black in the source space is mapped to the value of black in the destination space, so that the full tonal range of the destination space is used and the darkest black possible is maintained. blend mode A method of blending the pixel values for two or more images (generally comprised of two or more layers on a multi-layered document) to produce new values. Blend modes typically involve a particular algorithm that is used to calculate a new result based on the pixel values of the layers being processed. For example, Adobe Photoshop includes an overlay blend mode where brightness values in the upper image layer that are brighter than 50% gray will produce a result that is lighter than the pixel value on the underlying image layer, and values darker than 50% gray will produce a result that is darker than the pixel value on the underlying image layer. Blu-ray Disc An optical disc format originally designed to enable the playback of high-definition (HD) video as well as providing a method of storing relatively large amounts of data. A Blue-ray Disc can store 25GB with a single-layer disc or 50GB with a dual-layer disc. The Blu-ray Disc format was developed by the Blu-Ray Disc Association, which includes a variety of high-tech companies as members. blur The visible effect of a loss of contrast along contrast edges in an image. Blur can be caused by improper focus, subject or camera movement with a relatively slow shutter speed, software processing of an image, or other causes. While blur in an image is often seen as a negative factor in terms of overall image quality, it can also be used for creative effect. bokeh A term that refers to the appearance of out-of-focus points of light within a photographic image. These points of light are generally rendered as bright translucent areas within the image, often with a circular (or nearly circular) shape. The specific attributes of a given lens impact how bokeh is rendered. bracketing The process of capturing multiple exposures of a single scene with different exposure settings. Bracketing generally involves capturing one or more images that are darker and brighter than a baseline exposure. By bracketing exposures you can later choose which exposure is optimal for the conditions, and also blend multiple exposures together into a high dynamic range (HDR) image that maximizes the amount of information that can be presented in a single image of a scene that contains a wide range of tonal values. Many cameras allow you to automatically bracket exposures, though the process can also be done manually. 10

11 brightness A measure of the amount of light reflected or emitted, generally (though not always) described as a percentage, where 0% is black and 100% is white. See also lightness and luminance. bronzing A phenomenon where certain inks (often black) have reflective properties that cause them to have a slightly bronze appearance under certain lighting conditions. This phenomenon is often confused with metamerism. See also metamerism. bulb An exposure mode available on many cameras that enables you to manually control the length of the exposure by holding the shutter release button until you want to stop the exposure, sometimes limited to a maximum of 30 seconds unless a cable release is employed. burning A technique traditionally used in film photography whereby certain areas of a silver-based print are darkened by allowing more light to reach those areas (by blocking all other areas of the image) during exposure. The same effect can be created using a variety of software tools and techniques when optimizing the digital image after capture. bus-powered A term for a device (such as a hard drive) that obtains power directly from the computer interface to which it is connected (such as USB or FireWire ) and thus does not require a separate power connection. byte Generally a group of eight bits (digits) comprising a single value in a computer system. A byte is generally able to represent a single character such as a letter or number, and thus is a building block for information stored and processed by computers. 11

12 C cable release A device that can be connected to a camera and then used to trigger the shutter for an exposure. Many cable releases include a variety of other advanced features including the ability to captured bracketed exposures, create longer exposure than the camera is normally capable of, or capture interval exposures for purposes of creating a time-lapse video. cache A store of information generally used for temporary purposes by software, generally for purposes of speeding up the processing of certain tasks. calibration The process of adjusting settings (such as brightness and contrast) in order to change the behavior of a device to match established standards. Calibration is performed before profiling a device, reducing the amount of compensation the profile must apply to the device. A common example is the process of calibrating and profiling a monitor display in order to ensure the most accurate results possible. See also profiling. camera A device, often used in conjunction with film or a digital image sensor as well as some form of optic to create a photographic record of the light reflected from or emitted by a scene. camera back A general term for a device that attaches to the back of a camera, containing either the film for exposure (a film back) or a digital image sensor (digital back). See also digital back and film back. camera profile A color profile that describes the color behavior of a digital camera so that the colors can be corrected by assigning that profile to the captured image. A profile is specific to the specific camera, exposure settings, and lighting conditions, so camera profiling is not practical for photographers who photograph under variable lighting conditions, such as outdoor photographers. It can be beneficial when many photographs are captured under the same lighting conditions, as may be the case for studio photographers. candela A unit of measure for luminosity. One candela is equal to 1/60 of the luminosity per square centimeter of a blackbody radiating at 2046 Kelvin. See also color temperature and Kelvin. 12

13 card reader A device that enables you to transfer digital photos and videos from the digital media card used in the camera to a computer or other device. catalog A general term for a database of information, which in the context of a digital photography workflow would contain information about the images being managed or processed by the software utilizing the catalog. cathode ray tube A type of vacuum tube that enables the display of illuminated information on a conventional computer monitor or television set. This technology has been largely replaced by various flatscreen technologies, such as the LCD (liquid crystal display). CCD See charge-coupled device. CD An acronym for compact disc. See also compact disc. CD-R A type of compact disc upon which data can be recorded using a suitably equipped compact disc drive. Once data is written to a CD-R disc it cannot be changed. CD-RW A type of compact disc upon which data can be recorded using a suitably equipped compact disc drive. Within certain limitations, data can be re-written to a CD-RW drive, enabling the information stored to be changed. center-weighted average metering A metering mode whereby the full viewfinder area is evaluated when calculating exposure, but with an emphasis placed on the central area of the frame. central processing unit The primary component of a computer responsible for processing the majority of calculations and program instructions called for by the operating system or software. channel An individual component of a digital image that describes various attributes of the image on a per-pixel basis. For example, the red channel in an RGB image contains values representing the amount of red light for each pixel. The three color channels (red, green, and blue) in an RGB image together describe the full color of each pixel. Channels can also describe other attributes of an image on a per-pixel basis, such as opacity or degree of selection for each pixel. 13

14 characterization Typically referred to as profiling, characterization is the process of gathering information about the color behavior of a device (generally by making measurements with a calibrated sensor) and assembling that information into a data file (the profile) that allows compensation for the device behavior to produce more accurate color. charge-coupled device A device that enables the processing of an electric charge, often employed in digital camera image sensors to convert light energy into an electric charge that can be measured and stored by the digital camera. See also complimentary metal-oxide semiconductor. chroma The property of a color that describes its purity relative to the primary colors. With higher purity, a color will appear more saturated, while with lower purity it will appear more dull. Chroma is one of the attributes in the LCH (lightness, chroma, hue) color model. Many photographers use the term saturation rather than chroma. See also saturation. chromatic aberration Color artifacts typically exhibited as colored fringing along high-contrast edges in a photo, generally caused by different wavelengths of light being focused on a different focal plane. circle of confusion The result of light rays not being in perfect focus, which creates a spot rather than a single point. The circle of confusion is a key factor in calculating depth of field, which is generally defined as the region where the size of the circle of confusion is smaller than the resolution of the human eye or the display medium. clipping The loss of detail in the brightest highlights or darkest shadows of an image. Clipping can be caused by an improper exposure for the original capture, or by adjustments in image-processing software. Many image-processing software applications provide means for viewing which areas of an image exhibit clipping of highlight or shadow detail. See also clipping preview. clipping preview A feature of various software tools that enables you to see an indication of which areas of a photo have a loss of detail in the brightest highlights and/or the darkest shadows. See also clipping. closeup photography Photography involving subjects that are focused very close to the lens, resulting in a subject that appears relatively large within the frame, though smaller than life size relative to the capture medium. If the subject appears life size or larger in the image, relative to the capture medium, then that photography would be considered macro photography rather than closeup photography. See also macro photography. 14

15 cloud A term that commonly refers to a system whereby software or data is stored on remotely located computers that are connected to the Internet, thus accessible by any other computer with proper permission that is also connected to the Internet. CMOS See complimentary metal-oxide semiconductor. CMYK A color model based on the subtractive primary colors of cyan, magenta, and yellow, with black added so that the final output can contain pure blacks. This color model is used to describe how much ink of each color is required to produce a given final color in a print. codec Software or hardware that encodes or decodes information, often used in the context of digital video. The word codec is formed from the separate words coder and decoder, which represent the key roles of a codec. See also coding and decoding. coding The process of encoding (or compressing) digital information. An example would be digital video, which can be encoded to a particular video format, but then decoded for playback. compact disc A disc that utilizes optical and laser technology to store information. A standard compact disc can store 700MB of information. complimentary metal-oxide semiconductor (CMOS) A technology employed in the manufacture of integrated circuits for various microprocessor applications. Many digital cameras employ CMOS semiconductors as a key component of the image sensor that captures the actual image data. See also charge-coupled device. collar See lens collar. color A response in the human visual system based on an interpretation of light at different wavelengths. The range of colors that humans can perceive is the visible spectrum. See also visible spectrum. color gamut A definition of the range of color values available. For a device (such as a digital camera or printer), this is the range of colors that can be captured or displayed. In the context of a color profile, the color gamut describes is the range of colors that are available to use within the image. 15

16 color management A system that provides a variety of solutions to help ensure colors are produced and translated accurately across a variety of devices. Color management revolves around profiles that describe the color behavior of the devices in a workflow, so that color values can be interpreted between devices. A good color management workflow allows you to produce predictable and (to the extent possible) accurate output. color model A method of describing color using numeric values for specific attributes. Examples include RGB (red, green, blue), CMYK (cyan, magenta, yellow, black), HSL (hue, saturation, lightness), LCH (luminance, chromaticity, hue) and Lab (lightness, a, and b ). See also RGB, CMYK, HSL, LCH, and Lab. color profile See ICC profile. color space The range of colors available for a particular color model or profile, often defined based on a working space profile. The color space represents the range of colors available for a particular image during editing. See also working space profile. color spectrum A range of color values, often taken to mean the range of colors in the visible spectrum. See also visible spectrum. color temperature The color component of light, measured in degrees Kelvin. Lower color temperatures correspond to the hues we think of as being warm colors (reds to yellows) and higher temperatures correspond to the hues we think of as cool (greens to blues). See also Kelvin. color wheel A graphical display of the relationship between colors in the visible spectrum, typically presented with colors displayed around a circle. Red generally defines zero degrees at the top of the color wheel. colorimeter An instrument that measures the relative intensities of red, green, and blue light, often used to measure colors from a monitor during the process of calibrating and profiling. ColorSync The color management system included in the Apple Macintosh operating system. See also color management. 16

17 CompactFlash A storage device format typically employing flash media for storage, but in some cases also employing hard drive storage technology. The CompactFlash format has become widely used among digital cameras for storing images as they are captured. The CompactFlash trademark is owned by the CompactFlash Association. complementary colors Colors that are generally perceived as being pleasing to the eye when used together, in part because of their relationship on the color wheel. For example, colors on opposite sides of the color wheel from each other (such as blue and yellow) tend to complement each other. Complementary colors can also have different relationships on the color wheel, and are not limited to only two colors. For example, a triadic set of colors includes three colors that are equally spaced around the color wheel, which also tend to be perceived as harmonious. compression The process of describing information in a format that enables that information to be described with less data. Compression is often used to reduce the size of image files. The compression can be lossy, which causes detail and quality to be reduced to some degree in order to achieve a smaller file, or lossless where the data is described in a simpler way without changing the actual data. See also lossless and lossy. compression artifacts Visible artifacts in an image caused by compression that is not lossless. See also artifact. continuous auto focus An automatic focusing mode whereby the camera constantly re-evaluates the focus for the subject being focused upon. Continuous auto focus is especially helpful when photographing moving subjects. continuous tone A term describing an image reproduced with a continuous range of tonal and color values, theoretically with an infinite number of possible tonal or color values. Most commonly used methods for printing digital photos, such as inkjet printers, blend various inks together to simulate a broad range of colors, and therefore would not be considered continuous tone. Traditional photographic prints and prints produced with dye sublimation printers provide continuous tone output. contrast The presence of differences of tonal values between pixels in an image. High contrast is exhibited by a relatively large difference between tonal values, while low contrast is exhibited by a relatively small difference between tonal values. Perceived contrast can also be increased when the transition between pixel values occurs across a relatively short distance within the image. 17

18 convert profile The process of changing the profile that will be used to translate the color numbers in an image file so those numbers relate to specific colors. When you convert an image from one profile to another, the color numbers are changed so that when interpreted based on the new profile the colors will maintain their same appearance to the extent possible. The rendering intent used to convert from one profile to another determines how colors outside the destination gamut are dealt with. copyright An exclusive legal right to content that benefits the creator of that content. Specific rights and protections under copyright law vary by country. core An individual processor within a central processing unit that contains multiple processors. Such an architecture can improve overall system performance since multiple tasks can be processed concurrently. CPU An acronym for central processing unit. See also central processing unit. crop factor A term describing the effect upon the behavior of a camera and lens combination due to the size of the image sensor. Most frequently a crop factor refers to the use of a lens designed for a 35mm camera system on a digital camera with an image sensor smaller than a single frame of 35mm film. The result is the cropping of the image circle projected by the lens, creating a field of view that matches a lens of a longer focal length. For example, if a particular image sensor has a crop factor of 1.6X relative to a frame of 35mm film, a 100mm lens would produce the same field of view as you would otherwise achieve with a 160mm lens on a 35mm film camera. See also focal length multiplier. CRT An acronym for cathode ray tube. See also cathode ray tube. Curves An adjustment available in Photoshop and other image-processing software applications that enables you to exercise a high degree of control in altering the brightness and contrast in a photo. Anchor points are used to lighten or darken ranges of tonal values in the image, with smooth transitions in the adjustments defined by curved lines connecting each anchor point. The same controls can be used to modify overall color in the photo by adjusting the individual color channels. 18

19 D D50 A standard illumination source with a color temperature of 5000 degrees Kelvin. This is the standard illumination source for prints assumed in a typical color management workflow. The D50 standard is also used to describe lights used when evaluating the accuracy of printed images. D65 A standard illumination source with a color temperature of 6500 Kelvin. This is the a common standard used for calibrating monitors in a color-managed workflow, because the slightly cool appearance is generally close to the native color temperature of monitor displays. d-max A measure of maximum density, generally used to describe the maximum black that a particular film can achieve. daisy chain A serial connection of computer peripherals. For example, the FireWire interface enables you to connect a device to a computer, then another device to the first device, and another device to the second device, and so on, up to a limit of 63 FireWire devices. dark noise Noise that results from the image sensor separate of the recording of light during exposure, and generally related to heat buildup on the image sensor. decoding The process of decompressing data that has been compressed. For example, video can be decoded for playback based on the compression scheme or video format that was used to encode the video. demosaicing The process of calculating the full-color pixel values for an image captured in a RAW file format. With most digital camera image sensors each pixel within the capture only has a single color value, such as either red, green, or blue for a typical RGB capture. In the RAW conversion process, the remaining values are calculated through a form of interpolation. For example, if a particular pixel only contains a red value, during the RAW conversion process the green and blue values will be calculated for that pixel, producing the actual RGB color for that pixel. Demosaicing is also referred to as RAW conversion or RAW processing. See also RAW conversion. 19

20 densitometer An instrument that measures the density of a sample, often used to measure the density of dye in photographic film or of ink on paper. depth of field The range within a scene that is rendered in acceptable focus. More technically, depth of field is the region where the size of the circle of confusion is smaller than the resolution of the human eye or the display medium. Factors that influence the range of depth of field include lens aperture, lens focal length, and distance to subject. See also circle of confusion. destination profile The ICC profile that is being used to interpret colors in an image when the color information in that image is converted from a different profile. The profile being converted from is referred to as the source profile. See also convert profile and destination profile. device-dependent color space A color space where the actual colors available depend on the device being used for output. For example, a device-dependent printer profile would provide a range of colors that are determined by the capabilities of the printer, ink, and paper combination for which the profile was created. A device-dependent color space would generally only be used when preparing an image for final output. See also device-independent color space. device-independent color space A color space where the colors are described based on how the human visual system perceives colors, so that the actual color is described accurately, without the need to know what type of device will be used to produce the color. Device-independent color spaces (such as Lab) are used as the translation space when converting colors between profiles. See also devicedependent color space. diffraction The spreading or scattering of light waves, which in the context of photography is generally caused by the interference of the lens aperture through which the light is traveling. diffuser A material used to spread light evenly, creating a softer light source that results in shadows that are not as strong as with a direct light source. digital A system by which information is stored and transmitted using discrete values. This contrasts with an analog system where the signals being measured or recorded are continuously variable. See also analog. digital back A camera back that utilizes a digital image sensor to record a photographic image. A digital back is 20

21 generally used with medium format or larger cameras that utilize a camera back separate from the camera as a container for the film or digital image sensor used to record a photographic image. Digital Negative A publicly available file format developed by Adobe and designed to provide an archival format for storing RAW capture data recorded by digital cameras. The Digital Negative format is often referred to as DNG, and the default filename extension for this file format is.dng. digital single-lens reflex camera A single-lens reflex (SLR) camera that makes use of a digital image sensor rather than film for recording the image projected by the lens. See also single-lens reflex camera. digital video disc An optical disc format designed for storing a larger amount of data than the compact disc format that preceded it. A single-layer one-sided disc can store 4.7GB of data, while a dual-layer double-sided disc can store 17GB of data. The digital video disc format is sometimes referred to as digital versatile disc, and is most often referred to by the acronym DVD. direct light See incident light. dithering The process of arranging pixels or dots (such as droplets of ink) of colors to simulate tones or colors that are outside the color gamut of a given device or color space. Dithering helps achieve the appearance of a higher tonal or color range, and can also help prevent the appearance of posterization in an image. See also posterization. disc A term generally used to describe optical storage media, as opposed to hard drive or floppy drive storage technology, which is referred to as a disk. See also disk. disk A term generally used to describe hard drive or floppy drive storage technology, as opposed to optical storage media, which is generally referred to as a disc. See also disc. dispersion The splitting of light into different wavelengths, which in the context of photographic lenses can lead to the appearance of chromatic aberrations in the captured image. Many lenses use lowdispersion glass to improve overall image quality. See also chromatic aberration. display adapter A component of a computer or other device that processes the information used to create the luminance and color values shown on a display such as a monitor. The display adapter is often referred to as a video card. 21

22 DNG An acronym for the digital negative file format. See also digital negative. dodging A technique traditionally used in film photography whereby certain areas of a silver-based print are lightened by holding back light so it does not reach those areas (by blocking the light with an object) during exposure. The same effect can be created using a variety of software tools and techniques when optimizing the digital image after capture. dot A term generally used in the context of printing that describes the density of information being printed. That information density is generally referred to as the dots per inch (dpi) measure of resolution, which relates to the number of dots in a linear inch on the printed page. dot gain The spreading of ink on paper upon printing, which can cause a loss of sharpness, detail, and color fidelity in the print. dots per inch An indication of the density of the droplets of ink used to create the printed output for an image. This term is often confused with pixels per inch (ppi). See also pixels per inch. dpi An acronym (though one that is generally not capitalized) for dots per inch. See also dots per inch. droplet The smallest amount of ink that can be placed on a page by a printer, such as a photo inkjet printer. This droplet size is generally measured in picoliters, but often presented as a dots per inch value (such as 2,880 dpi) even though the droplets of ink are not the same as the standard measure of dots per inch for resolution or the pixel per inch resolution of the image being printed. DSLR An acronym for digital single-lens reflex cameras. See also digital single-lens reflex camera. dual-layer A term generally used to describe an optical disc such as a CD or DVD that contains two layers and thus is able to store a greater volume of data than a single-layer disc. duotone (1) A printing process where an image is reproduced using a halftone process where two contrasting ink colors are printed over one another. The result is an image with a greater range of middle tone and highlight values compared to a monochromatic print. (2) An image mode in Photoshop that enables you to create images comprised of two base 22

23 colors defined by the user. See also tritone and quadtone. DV A format for recording and playback of digital video, employed by a wide variety of digital video cameras. DVD An acronym for digital video disc. See also digital video disc. DVD-R or DVD+R A type of digital video disc upon which data can be recorded using a suitably equipped digital video disc drive. Once data is written to a DVD-R disc it cannot be changed. The + versus - designations refer to slightly different formats of the DVD media. DVD-RW or DVD+RW A type of digital video disc upon which data can be recorded using a suitably equipped digital video disc drive. Within certain limitations, data can be re-written to a DVD-RW drive, enabling the information stored to be changed. The + versus - designations refer to slightly different formats of the DVD media. dye sublimation A type of printer that uses the process of sublimation to impregnate a solid dye into the surface of a paper surface by converting the dye directly from a solid to a gas form. Despite the durability of the prints produced by a dye-sublimation printer, these types of printers have not become especially popular among photographers. dynamic range A measure of the range between the darkest and brightest values possible, often described as a range of exposure values found in a scene, or the range of exposure values a digital camera is able to faithfully record. 23

24 E E-TTL An acronym for Evaluative-Through the Lens metering, which is a Canon metering technology for flash photography. An updated version of E-TTL is known as E-TTL II, and an earlier version was known as A-TTL. EIDE An acronym for Enhanced Integrated Drive Electronics. See also Enhanced Integrated Drive Electronics. embedded profile A profile included within an image file that provides information on how to translate the color numbers stored in the image and makes it possible to always render accurate color for the image. encoding The process of compressing data or otherwise processing that data to a particular data format. For example, digital video can be encoded using a particular video format and compression scheme. Enhanced Integrated Drive Electronics An update to the original Integrated Drive Electronics standard for hard disk drive data connections, developed by Western Digital to include the use of direct memory access by the hard disk drive. Ethernet A system for connecting multiple computers so they can share data, as well a term used to describe the cable used to connect a computer to such a network. In common practice an Ethernet cable is a primary method for connecting a computer to the Internet. EV An acronym for exposure value. See also exposure value. evaluative metering mode See multi-zone metering. exposure A term used to describe both the relative brightness of a photographic capture, as well as the combination of settings (lens aperture, shutter speed, and ISO setting) used to adjust the brightness of the photograph. 24

25 exposure latitude A term used to describe the dynamic range that a particular digital camera is capable of rendering in a single photographic capture. The exposure latitude of a digital camera is generally described as a number of stops, which describes the number of stop of light that can be captured in a single image. See also dynamic range. exposure value A general measure of brightness values within a scene. Exposure values are generally referred to as stops of light, with reference to the term f-stop. One stop brighter represents twice as much light as the baseline value, while one stop darker represents half the amount of light. See also f-stop. Extended Graphics Array A video display standard originally released by IBM in 1990, generally referred to by the acronym XGA. While XGA represented resolutions of both 800x600 pixels and 1024x768 pixels, in common use the term XGA refers to the higher 1024x768 resolution. extension tube A device that can be mounted between the camera and lens, positioning the lens further away from the camera. This enables the focus point to be positioned closer to the subject than would be possible with the lens mounted directly to the camera. Some light is lost when an extension tube is used, requiring compensation with exposure settings. An extension tube generally includes connections so that all lens functions will continue to operate normally. 25

26 F f-stop A measure of the size of a lens aperture relative to the focal length of the lens, calculated by dividing the lens focal length by the effective aperture diameter. As such, the f-stop defines the relative amount of light projected to the image sensor, enabling photographers to calculate exposure adjustments based on aperture size. The f-stop is effectively a fraction, often presented as f/8, for example, to define a lens aperture with a diameter equal to 1/8th the lens focal length. feathering A process of blending one image component into another with a smooth and gradual transition. That blending can involve two images forming a composite final result, the effect of an adjustment that is being applied only to a specific area of the image, the edge of a selection identifying a particular area of an image, or other components. As an example, you can think of a digital brush with a hard edge as not exhibiting any feathering, and a brush with a soft edge as exhibiting the effect of feathering. Fibre Channel A network topology primarily used for connecting data storage devices, offering one gigabit per second data transfer speeds. file system A system of organizing the individual files and folders on a storage medium. As an example, all computer operating systems utilize a file system to manage the files and folders contained on the storage devices accessible to the computer. film A general term for a medium coated with a light-sensitive emulsion for purposes of recording light as a photographic image. film back A camera back that holds film for the purpose of recording a photographic image. A film back is generally used with medium format or larger cameras that utilize a camera back separate from the camera as a container for the film or digital image sensor used to record a photographic image. filter A mechanism for changing the appearance of an image. In the context of a camera a filter can be placed in front of the lens to alter in some way the light that passes through the lens. In the context of computer-based software a filter is a set of algorithms applied to alter the appearance of a digital image. 26

27 FireWire The term used by Apple for their high performance interface based on the IEEE 1394 standards. The FireWire 400 interface can transfer data at up to 400 Mbps (megabits per second), and the FireWire 800 interface can transfer data at up to 800 Mbps. See also IEEE 1394a and IEEE 1394b. firmware Software that is included on a memory chip or other storage on an electronic device and controls some of the functions of that device. fisheye lens A lens with an extremely wide-angle field of view, in some cases capturing an image of a full 180-degree view. flare See lens flare. flash A device for illuminating a subject with artificial light, either as primary or supplemental light. Flash See Adobe Flash. flash media A form of non-volatile computer storage, such as that used to store images captured by digital cameras. flash synchronization The ability of a camera to synchronize the firing of a flash unit so that the illumination from the flash occurs within the duration of the shutter being opened during exposure. To achieve synchronization with the flash, many cameras limit the shutter speed at which flash synchronization can occur, commonly setting a limit of 1/125 th or 1/250 th of a second. See also high speed sync. flat-panel display A digital display that is relatively thin (flat) from front to back, such as the common LCD displays. This contrasts with the relatively deep form factor required for earlier CRT displays. focal length A measure of the optical power of a lens, generally defined as the distance from the front lens element to the point where the light rays are brought into focus. focal length multiplier A term describing the effect upon the behavior of a camera and lens combination due to the size 27

28 of the image sensor. Most frequently a focal length multiplier refers to the use of a lens designed for a 35mm camera system on a digital camera with an image sensor smaller than a single frame of 35mm film. The result is the cropping of the image circle projected by the lens, creating a field of view that matches a lens of a longer focal length. For example, if a particular image sensor has a focal length multiplier factor of 1.6X relative to a frame of 35mm film, a 100mm lens would produce the same field of view as you would otherwise achieve with a 160mm lens on a 35mm film camera. See also crop factor. focal point The point at which light rays converge to create an image that is in sharp focus. focus The quality of having light rays converged, resulting in an image that appears sharp. focusing rail A device that enables a camera to be gradually shifted in position closer to or further away from a subject in order to adjust focus. A focusing rail is most commonly used in macro photography where narrow depth of field requires very small adjustments in focus. Four Thirds system A digital camera format developed by Olympus and Eastman Kodak, combining image sensor and lens interchange specifications to effectively define a complete camera system. The sensor in a Four Thirds system has an image area of 17.3 x 13mm, with an aspect ratio of 4:3. fresnel lens A thin lens comprised of concentric rings that form a segmented lens, and which is commonly used to focus light into a smaller area. For example, many flash devices and certain flash accessories employ a fresnel lens to focus the light of the flash into a smaller area and enable that light to be projected at a greater distance. front focus A situation where a camera and lens combination tends to focus in front of the point at which focus was established. See also back focus. full-frame sensor A digital camera image sensor with an image area that has the same physical dimensions as a frame of 35mm film (36 x 24mm). full-spectrum A term that describes light representing the full spectrum of visible light. 28

29 G gamut See color gamut. gamma A term that refers to the average slope of a curve defining the relationship between tonal values and the perceived brightness of those values. In the context of a computer display, a gamma value of 2.2 is considered to be perceptually uniform and is the recommended target for monitor calibration. See also perceptually uniform. gamma correction The process of applying an adjustment to an image based on a curve defining the relationship between initial and final values. For example, a gamma correction is necessary to translate the linear response of the image sensor in a digital camera to the non-linear response of the human visual system. GB An acronym for gigabyte. See also gigabyte. gel A translucent material with a color tint that is used to alter the color appearance of a light source illuminating a subject to be photographed. gigabyte One billion (1,000,000,000) bytes of information, generally used in the context of storage capacity or file sizes for a computer system. GIF An acronym for the graphics interchange format file format. See also graphics interchange format. gimbal A mechanism that allows for freedom of movement in multiple directions. In the context of photography, a gimbal head is often used in conjunction with a tripod to enable a photographer to quickly pan with a moving subject such as a bird in flight. global positioning system A system of satellites used to determine the position (latitude and longitude) of a receiver. The global positioning system can be used for (among other things) determining the position from 29

30 which a photograph was captured. glossy A shiny and smooth surface, which in the context of photography generally relates to the surface type of paper used for printing an image. GPS An acronym for global positioning system. See also global positioning system. GPU An acronym for graphics processing unit. See also graphics processing unit. graphics processing unit A processor that is a component in a display adapter (video card) that processes information related to the display projected by the computer. graduated split neutral density filter A filter that can be placed in front of a lens that is clear on one end and darkened on the other end, with a smooth gradation between the two. This allows the exposure for a bright area (such as the sky) to be held back in order to even out the overall exposure of a scene. gray balanced The property of a color model or profile where equal values of red, green, and blue correspond to a neutral gray value. gray card A card that is colored with an even shade of gray that reflects 18% of light hitting it. A gray card can be used as the basis of exposure calculations via a light meter, such as the meter built into most digital cameras. The actual 18% gray tonal value is the same as 50% gray ( middle gray ) in digital imaging software. grayscale A general term for a range of shades of gray, and also a color system that supports images with only a single channel, and thus can only support black and white images but not color images. 30

31 H halftone A printing technique where the image is reproduced by a series of dots, with various shades being simulated by varying the size and spacing of those dots. Multiple halftone patterns can be printed one over the other to expand the range of color values that can be printed. For example, a typical halftone printing process utilizes cyan, magenta, yellow, and black (CMYK) inks to create full-color output. See also CMYK. halo A relatively bright glow around the edge of an object or other contrast point in an image. As an example, applying excessive sharpening to an image can create halos along contrast edges in the image. hard drive A storage device that typically uses multiple platters that utilize magnetic fields to store data. hardware The physical components of a computer or other electronic device. Harris shutter A mechanism that incorporates colored filters (generally red, green, and blue) and that allows for the successive capture of individual primary color components for a scene at a delayed time interval. This leads to images where static objects appear normal, but moving objects appear with various color artifacts. The mechanism and process is named for Robert S. Bob Harris of Eastman Kodak, who developed the device and process. HD See high-definition. HDMI An acronym for High-Definition Multimedia Interface. See also High-Definition Multimedia Interface. HDR An acronym for high dynamic range or high dynamic range imaging (sometimes referred to as HDRI). See also high dynamic range imaging. 31

32 HDV A format for recording and playback of high-definition digital video, employed by a wide variety of digital video cameras. HDV is a trademark of JVC and Sony. hex key A tool used to drive bolts or screws with a hexagonal-shaped recess in the head. Bolts with a hexagonal recess are often employed by camera plates, ball heads, and other accessories, necessitating the use of a hex key. A hex key is often referred to as an Allen key or Allen wrench, with the Allen name being a registered trademark currently owned by Apex Tool Group. high definition A term that refers to a higher degree of information, often used in the context of video to describe video with a higher resolution than preceding video standards. By current standards high-definition video generally refers to video with a resolution of 1920x1080 pixels. High-Definition Multimedia Interface A digital interface for transmitting audio and video signals between compatible devices, commonly used for computer monitors and digital projectors. high dynamic range imaging The process of capturing multiple images of the same scene using different exposure settings (see bracketing) and then blending those exposures together with special software to create a single image that represents the full range of tonal values from the scene compressed into the range of a single image. high speed synchronization A feature that enables you to use flash synchronization at shutter speeds faster than the standard limit of your camera. When high speed synchronization is employed the flash duration is extended, generally by flashing many times per second for the full duration of the shutter speed. See also flash synchronization. highlight tone priority mode An option on certain Canon digital cameras that helps protect detail in highlight areas of an image. With this option enabled the actual dynamic range of the image sensor is not increased, but rather the captured image data is processed in such a way as to minimize the loss of perceived detail in highlight areas. histogram A graph that displays the distribution of luminance values in a digital image. This graph can be used to aid in evaluating exposure and adjustments for digital photos. You can display a histogram for an image both on the LCD display of the camera and using various software tools on a computer. Black is represented at the far left, and white at the far right, with an even distribution of tonal values in between. In many cases you can view both a luminance histogram as well as histograms for the individual color channels for an image. 32

33 history A record of the adjustments that have been applied to a digital image, generally with the ability to step back in history to undo one or more steps. In some software (such as Lightroom) the history is preserved for an image, whereas with other software (such as Photoshop) the history is volatile and lost when an image is closed. history state A specific step included as part of the history of tasks performed while processing a digital image in software used to process the image. hot light A light used to provide illumination to a subject that can be left on for an extended duration. This is different from a flash (or strobe) that only provides light for a very short duration. hotspot An area within range of a router providing Internet access. HSB A color model where color is described based on relative values of hue, saturation, and brightness. See also hue, saturation, and brightness. hue The property of color that we identify with the name of the color, such as red, green, blue, or any other possible color, separate of saturation and brightness for the color. Hue is generally described as the number of degrees around a color wheel, starting at zero degrees for red. Hue is one of the attributes in the HSB (hue, saturation, brightness) and LCH (lightness, chroma, hue) color models. hyperfocal distance The distance between the closest object that is in focus and the lens of the camera when that lens is focused at infinity. 33

34 I ICC See International Color Consortium. ICC profile A data file in a standard format defined by the ICC that describes the color behavior of a specific device. This allows color management systems to maintain consistent color throughout the complete color-managed workflow and across computer platforms. ICM See Image Color Matching. IDE An acronym for Integrated Drive Electronics. See also Integrated Drive Electronics. IEEE 1394a A high-speed interface specification that provides throughput speeds up to 400 Mbps, implemented by Apple as FireWire 400. IEEE 1394b A high-speed interface specification that provides throughput speeds up to 800 Mbps, implemented by Apple as FireWire 800. Image Color Matching The color management system included in the Windows operating system, often referred to by the acronym ICM. image sensor A general term for the image sensor on a digital camera that is sensitive to light, and thus able to create a digital photographic image from the light passing through the lens of the camera. image stabilization A feature of various lenses and cameras that compensates for movement of the camera and lens system to achieve sharper images. The various implementations of image stabilization technology by different manufacturers include Optical Image Stabilizer (IS) from Canon, Vibration Reduction (VR) from Nikon, and Optical Stabilization (OS) from Sigma, among others. 34

35 incident light Light that illuminates a subject directly from a light source such as a flash or hot light, often referred to as direct light. See also ambient light. infrared A range of electromagnetic radiation that has a wavelength just above the limits of the visible spectrum. Certain films and digital cameras are capable of recording infrared energy, which often creates images that have a surreal quality to them. infrared cutoff filter A filter typically included in front of the image sensor on a digital camera, which reduces the amount of infrared energy reaching the sensor. The presence of an infrared cutoff filter can help prevent image problems, but also limits the ability of a digital camera to capture infrared photographs. infrared trigger A remote trigger that uses an infrared light beam as the basis of triggering an exposure. Such a trigger typically consists of a transmitter and receiver that are pointed toward each other. If an object (such as a moving animal) walks between the transmitter and receiver the infrared beam will be momentarily blocked and the exposure will be triggered. inkjet printer A category of printer that employs some means (usually vibration or electric current) to spray liquid ink onto the printing surface. Inkjet printers are commonly used to produce high-quality prints of photographic images. Integrated Drive Electronics An interface for hard drive data connections, later renamed to Advanced Technology Attachment (ATA). A notable feature of the IDE interface was that the hard disk drive controller was integrated with the hard disk drive rather than on the separate controller card. interlaced In the context of digital video or a digital display, a configuration whereby the overall image is created in two or more passes, with alternating lines of the image refreshed with each pass. This contrasts, for example, with progressive-scan video, where each line of the display is drawn in sequence. See also progressive. International Color Consortium A group of companies that develop industry-wide standards for color management, commonly referred to by the acronym ICC. For more information, see the ICC website at internet An interconnected network of computer networks, enabling a larger group of computers to share resources. 35

36 Internet A specific implementation of an internet that is widely used worldwide to share information among a wide range of servers and other computers and devices. interpolation The process of calculating a value that falls between two other values. In the context of digital photography, interpolation generally refers to the process of calculating pixels to be added between existing pixels when an image is enlarged. The term is often used to refer to the process of calculating pixel values when an image is made smaller, requiring that the total number of pixels be reduced. See also resampling and resizing. intervalometer A device that counts intervals of time. In the context of digital photography, this term generally refers to a cable release that includes an interval timer function, enabling the capture of multiple images at a set interval, such as for creating a time-lapse video. IR cutoff filter See infrared cutoff filter. ISO An acronym for the International Standards Organization, but more commonly used by photographers as a term related to light sensitivity for a recording medium such as film or image sensors. In the context of digital photography, ISO refers to the degree of amplification applied to the image data in order to achieve a smaller aperture or faster shutter speed. The potential impact of a higher ISO setting is more noise in the digital capture. IT8 target One of the standard target images used for calibrating and profiling scanners and printers. 36

37 J jaggies A slang term for jagged edge seen in elements of an image caused by the representation of curves or lines that are other than horizontal or vertical. This phenomenon is caused by the representation of these curves or lines using pixels that have a square (or rectangular) shape. See also aliasing and anti-aliasing. Joint Photographic Experts Group The committee that created the a variety of digital imaging standards, including the JPEG file format that shares the name of the organization. The JPEG file format utilizes lossy compression to reduce the file size of an image, with the option to determine the balance between file size and image quality. JPEG An acronym for the Joint Photographic Experts Group, which is both an organization and a file type created by the organization. See also Joint Photographic Experts Group. JPEG 2000 An image file format created by the Joint Photographic Experts Group that was originally intended to replace the original JPEG file format. Due to legal issues related to intellectual property rights concerns, the JPEG 2000 file format has not been widely adopted. JPG A shortened version of the JPEG acronym for the Joint Photographic Experts Group and the popular JPEG file format created by this organization. This shortened acronym is commonly used as a filename extension for JPEG images, since older operating systems often limited filename extensions to three characters. 37

38 K KB An acronym for kilobyte. See also kilobyte. Kelvin The unit of measure used to describe color temperature. One degree Kelvin equals one degree Celsius, but the Kelvin scale begins at absolute zero. As a result, 0 Kelvin equals 273 Celsius. For purposes of color management, the Kelvin scale is used to describe the color appearance of a white object. The scale used is based on the wavelengths of light given off by a theoretical black body radiator when it is heated. keywords Words that can be added to the metadata for a digital photo, and that can identify details about the subject and overall content of a photo. Keywords are especially helpful for situations where images containing specific subjects or meeting particular criteria must be located at a later date. kilobyte One thousand (1,000) bytes of information, generally used in the context of storage capacity or file sizes for a computer system. 38

39 L Lab A color model where each color is described based on values of lightness (L), color on a blue/ yellow axis (a), and color on a green/magenta axis (b). landscape orientation An horizontal orientation for a photo where the width is greater than the height. layer In the context of digital imaging software such as Photoshop, an image element that is separated from the underlying pixel data. For example, a composite image might contain multiple image layers, and any image might contain adjustment layers that define adjustments to be applied to the image. layer mask A construct that defines the visibility of an image layer or adjustment layer, allowing for the creation of composite images comprised of multiple individual images blended together, or targeted adjustments that affect only specific areas of a photo. A layer mask typically contains shades of gray that define the relative visibility of the layer associated with the mask. LCD An acronym for liquid crystal display. See also liquid crystal display. LCH A color model where color is described based on lightness, chroma, and hue. See also lightness, chroma, and hue. LED An acronym for light-emitting diode. See also light-emitting diode. lens (1) A transparent material, often glass, that incorporates curved sides for purposes of changing the convergence of light rays for purposes of focusing light, or for magnifying or shrinking the image projected by the lens. (2) A device that combines multiple lens elements to achieve a specific goal for projecting an image, such as to achieve high magnification or a particularly wide field of view. 39

40 lens collar A component that attaches to a lens (generally larger lenses with a relatively long focal length) and includes a bracket that can be used to mount the lens directly to a mount such as a ball head. Mounting a lens with a collar enables the weight of the camera and lens system to be more evenly distributed, reducing the strain on all of the components. lens element An individual lens used in a device, such as a camera lens, that features multiple lenses to achieve a specific goal for projecting an image. See also lens. lens flare Bright and often colorful areas within a photo caused when a bright light source is reflected among the internal optical elements of a lens. Specially designed lens shades can prevent lens flare when the bright light source falls just outside the image area for the lens. See also lens shade. lens shade A device that generally attaches to the front of a lens, shading the front element from bright light sources that fall just outside the image area for the lens. Such a lens shade can help eliminate the presence of lens flare. See also lens flare. Levels An adjustment in Photoshop that allows you to change the overall brightness and contrast in a photo. Individual adjustments are provided to set the black and white point based on the distribution of tonal values within the image, to change the overall brightness with a gamma (middle tone) adjustment, and to tone down the value of black and/or white using the Output Levels controls. The same controls can be used to affect overall color in the image by working with the individual color channels in the image. light A form of electromagnetic radiation that falls within the range of wavelengths that the human visual system responds too, and thus provides illumination. Visible light encompasses a range of wavelengths from about 380 nanometers to about 780 nanometers. light meter A device that is able to measure the intensity of light so that proper exposure can be calculated. A basic light meter is included in most (if not all) digital cameras, but you can also utilize a light meter separate from a digital camera. light-emitting diode A light source utilizing a semiconductor that is capable of producing a bright light with low heat and energy consumption. Light-emitting diodes are used as an illumination source in some flatpanel displays, among other uses. 40

41 light-field camera A camera employing a plenoptic lens that captures not only the intensity and color of the light projected by the lens, but also the direction of the light. Because of the additional information gathered by a light-field camera, a variety of post-processing capabilities exist, including the ability to refine depth of field after the capture. light painting A technique that involves capturing a long exposure under relatively low lighting conditions while using a strong light source (such as a flashlight) to paint with light across certain areas of the scene. lightness A measure of the amount of light reflected or emitted, generally described as a percentage where 0% is black and 100% is white. See also brightness and luminance. lightning trigger A remote cable release that senses lightning strikes and triggers an exposure for the camera, designed for the purpose of enabling photography that includes lightning strikes in the frame. linear A term used to describe a scale where, for example, doubling the intensity of light produces double the response (such as the perceived brightness). When relationships between input and output values are linear, plotting a chart that illustrates the relationship will form a straight line. The human visual system is very much nonlinear. See also nonlinear. linear DNG A file in the Adobe Digital Negative (DNG) format that has had the full color values calculated for each pixel. By contrast, a RAW DNG contains the information from a RAW capture by the camera which in most cases only includes one of three RGB (red, green, blue) color values for each pixel. See also digital negative and RAW DNG. linearization The process of calibrating a device to behave in a linear fashion, to that the response from the device is commensurate with the input received on a linear scale. See also linear. liquid crystal display A type of digital displays that makes use of liquid crystals to modulate the relative strength of light for each pixel on the display. Such displays are used in a wide variety of applications, including the various displays on a digital camera and many computer monitor displays. lithium-ion battery A rechargeable battery commonly used in digital cameras that employs lithium ions moving between positive and negative electrodes to provide or store electric power. 41

42 live view A feature on a variety of digital SLR cameras that projects the image from the image sensor onto the LCD display on the back of the camera, so you can see the actual image to be photographed before the image is captured. Such a display option can be helpful for evaluating composition and focus, for example. long exposure noise reduction An option in many digital cameras that applies additional noise reduction to images that were captured with particularly long exposures (generally around 30 seconds or longer) when noise caused by heat buildup is a particular concern. lookup table (LUT) See video lookup table. lossless A term used to describe a process that results in no change to the original data. A common example is lossless compression, which enables the file size for a digital photo to be reduced without actually changing any of the original information. lossy A term used to describe a process that results in a change to the original data (often a loss of detail and quality). A common example is lossy compression, which reduces file size by simplifying the description of the data contained in the file, but with some change to the original data in the process. luminosity A measure of the amount of light emitted, generally described as a percentage where 0% is black and 100% is white. See also brightness. luminosity mask A type of layer mask that defines areas of the image based on original luminance values for pixels within the image. For example, a luminosity mask could be created for purposes of applying an adjustment that only affects the brightest areas of a photo. See also layer mask. luminance See luminosity. luster A term commonly used to describe a semi-gloss paper surface, which is a surface that is glossy but without as much reflectance as more typical glossy surfaces. See also semi-gloss. LUT An acronym for lookup table, which generally refers to the video lookup table that is a component in a display adapter. See also video lookup table and display adapter. 42

43 M macro lens A specialized type of lens that is able to focus very close to the front lens element, often used for closeup or macro photography. macro photography Photography involving subjects that are focused very close to the lens, resulting in a subject that appears relatively large within the frame. Macro photography is generally defined as the photography of subjects that appear life size or larger in the image, relative to the capture medium. So, for example, if a subject photographed on 35mm slide film appears on that film to be the same size or larger than the actual subject, the image would be considered macro photography. See also closeup photography. manual exposure mode A camera setting that requires the photographer to establish the lens aperture and shutter speed settings manually, generally by reference to the camera s exposure meter. manual focus mode A camera setting whereby automatic focus will be disabled, requiring the photographer to manually focus the lens. matte A surface with a relatively low reflectance. Matte papers, for example, do not have as high a reflectivity as glossy papers, leading to reduced glare but also lower dynamic range and saturation in the printed image. See also glossy. matrix metering mode. See multi-zone metering. MB An acronym for megabyte. See also megabyte. mean time between failures A measure of the average time between expected failures of a device, commonly used as a benchmark for the average reliability of digital storage devices such as hard disk drives. megabyte One million (1,000,000) bytes of information, generally used in the context of storage capacity 43

44 or file sizes for a computer system. megapixel A value equal to one million pixels, which is the most common method of describing the resolution of digital cameras. memory A general term for a storage medium, either volatile or non-volatile, used by digital devices. Examples include the volatile random access memory used for computer processing and the non-volatile flash memory used by digital cameras to record image files. memory card A storage device, typically employing flash-based memory, that enables you to store data. Various types of memory cards can be employed to store images as they are captured by digital cameras. memory color A color that the observer is familiar with through personal experience. It is particularly important that such colors in an image be rendered accurately. metadata Data that provides information about another set of data. In the context of photography metadata generally refers to the information about a digital photo that is stored within the image file itself. That metadata can include a wide variety of information including exposure settings recorded by the camera as well as other information added after the fact by the photographer. metamerism A phenomenon whereby two color samples appear to match each other under one lighting condition, but do not match under another lighting condition. metering The process of evaluating the light of a scene in order to calculate appropriate exposure settings. Micro Piezo The brand name of a piezoelectric technology employed by Epson printers that features small electric elements that vibrate rapidly in order to spray ink droplets onto the paper. This is contrasted with the thermal inkjet approach that utilizes heat to spray ink droplets. See also thermal inkjet. middle gray A shade of gray that is halfway between black and white on a linear scale. A value of 50 percent gray in a computer-based color system is the same as the 18 percent gray of a gray card. See also 18 percent gray, 50 percent gray, and gray card. 44

45 mirror lens A lens that employs mirrors in place of some lens elements in order to reduce size and weight at a given focal length. Mirror lenses are typically less expensive than traditional optical lenses, but tend to offer lower quality as well. model release A legal document that enables a photographer to demonstrate that they have permission to license, sell, or otherwise use an image that includes an identifiable person. moiré pattern An interference pattern that can result in artifacts in an image. Moiré patterns are most often found in photographs taken of fine detail and repeated lines in fabric. monitor A general term for a computer display. monitor profile An ICC profile that describes the color behavior of a monitor so that compensation can be applied to ensure a display that is as accurate as possible within the specific limitations of the monitor. monochrome A term meaning one color, generally used to describe a black and white image. Monochrome can refer to any image created using only a single color, with black being the most common color used to present a monochromatic image. monopod A camera support that consists of a single leg and a mounting point for a camera, providing a degree of stability that can ensure sharper images with a smaller footprint than a tripod. Moving Picture Experts Group An industry working group that establishes standards for audio and video compression and transmission. MP3 The common name for the MPEG-1 Layer III audio compression format developed by the Moving Picture Experts Group. MPEG An acronym for Moving Picture Experts Group. See also Moving Picture Experts Group. MPEG-4 A standard for audio/video content with high compression capabilities, developed by the Moving Picture Experts Group. 45

46 MTBF An acronym for mean time between failures. See also mean time between failures. multi-zone metering A metering mode for calculating exposure whereby the viewfinder image is divided into multiple zones, and those zones are evaluated individually to determine the overall best exposure settings. The specific implementation of multi-zone metering varies from one camera to the next, and often a degree of evaluation is performed in an effort to determine the type of scene being photographed in order to improve the exposure results. Multi-zone metering is often referred to as evaluative metering, matrix metering, and other names. 46

47 N nanometer A measure equal to one-millionth of a millimeter, which is used, for example, as a measure of wavelengths of visible light. nearest neighbor An interpolation algorithm that calculates the values of pixels to add during the enlargement of a digital image, in which only the neighboring pixel value is considered when determining the value of new pixels. The nearest neighbor interpolation algorithm is well-suited to the enlargement of simple graphics where crisp edges need to be maintained, but is not well-suited to enlarging photographic images. See also interpolation. network In the context of computers, a system that enables multiple computers to communicate with each other in order to share information, files, peripheral devices, or other components. neutral density filter A filter typically made of glass that can be placed in front of the lens and that reduces the amount of light passing through the lens without imparting a color cast. A neutral density filter enables you to achieve longer exposure times than would otherwise be possible. nickel-metal hydride battery A rechargeable battery commonly used in digital cameras that employs nickel oxyhydroxide electrodes much like a nickel-cadmium battery, but with negative electrodes that employ a hydrogen-absorbing alloy. noise The appearance of variations in pixel color and/or tonal values in a digital image. Noise is often caused by amplification of the digital signal due to a relatively high ISO setting in the camera. noise reduction The process of reducing the appearance of luminance and/or noise through processing of the data (such as in a digital photo). Noise reduction is employed in firmware in digital cameras and is also available in a variety of software applications. See also noise. nonlinear A term used to describe a scale where there is not a consistent relationship between input and output values. For example, with a nonlinear response doubling the intensity of light won t 47

48 necessarily produce double the response. When relationships between input and output values are nonlinear, plotting a chart that illustrates the relationship will form something other than a straight line. The human visual system is very much nonlinear. See also linear. normal lens A term that describes a lens with a field of view considered to match that of human vision, or more technically, a lens with a focal length that matches the diagonal dimension of the film or image sensor used to capture an image. For 35mm camera systems a 50mm lens is considered to be a normal lens. A normal lens is also sometimes referred to as a standard lens. nozzle The mechanism that sprays ink droplets from an inkjet printer. 48

49 O offset printing A printing process where ink is transferred from a metal plate to a rubber surface and then to the print medium. With color offset printing, multiple inks are used (generally cyan, magenta, yellow, and black), with each color printed individually, building up the final image as each additional color is applied to the print medium. See also CMYK. OLED An acronym for organic light-emitting diode. See also organic light-emitting diode. one-shot auto focus An automatic focusing mode where the camera establishes focus on a subject automatically, and then that focus does not change. The one-shot auto focus mode is useful for situations where the photographer wants to focus on a subject and then re-frame the scene. OpenGL The standard abbreviation for the Open Graphics Library standard. See also Open Graphics Library. Open Graphics Library A standard set of specifications for producing computer graphics, developed by Silicon Graphics and generally referred to as OpenGL. Many software applications make use of the OpenGL library to implement advanced graphics processing and displays. operating system Software that provides for the basic operation of a computer. The most commonly used operating systems are Microsoft Windows and Apple Macintosh. optical drive A storage device that utilizes optical media to store data. Laser light is used to illuminate the optical media, with variable reflectance used to determine the values for the data stored on the disc. organic light-emitting diode A form of light-emitting diode that utilizes a layer of organic compounds that emit light in response to an electric current. 49

50 orientation A description of the general relationship between width and height in an image. An image where the width is greater than the height is described as having a horizontal or landscape orientation, while an image where the width is less than the height is described as having a vertical or portrait orientation. out of gamut A condition where a color value is not within a defined color gamut. For example, an out of gamut color in the context of a print is a color that is included in the digital image but that the specific print, ink, and paper combination being used for printing is not capable of producing. See also color gamut. 50

51 P panning A photographic technique whereby the camera is moved to follow along with a moving subject, with the intent of tracking that subject so it will be rendered sharp in the photograph, even if the background is blurred due to the movement of the camera in conjunction with a relatively low shutter speed. panorama A type of photograph featuring a wide aspect ratio, where the final image is very wide relative to the height. A panoramic image can be created with a camera featuring a wide aspect ratio, by cropping an image with a standard aspect ratio, or by assembling multiple images into a composite panorama. See also aspect ratio. patent A form of intellectual property protection conferred by a government agency for an invention, with the owner of the patent having exclusive rights to that invention for a specified period of time. PCS An acronym for profile connection space. See also profile connection space. PDF An acronym for the portable document format file format. See also Portable Document Format. pellicle mirror A mirror that enables some light to pass through it while reflecting other light. Some digital SLR cameras make use of a pellicle mirror so that the mirror does not need to move in order to capture a photo or video. Utilizing a pellicle mirror offers certain advantages, such as the ability to employ continuous auto-focus, but also includes the disadvantage of less light reaching the image sensor. perceptual One of the four ICC rendering intents for handling out-of-gamut colors when converting colors from a source to destination profile. With the perceptual rendering intent, the full color gamut of the source space is compressed to fit into the destination space, maintaining the relationships between colors in the process. See also rendering intent. perceptually uniform A property where the distances between two colors in a color space relate to the perceived differences between those colors, so that across the full range of an adjustment the same amount 51

52 of adjustment has the same perceived effect. petabyte One quadrillion (1,000,000,000,000,000) bytes of information, generally used in the context of storage capacity or file sizes for a computer system. A petabyte is the equivalent of one million gigabytes or one thousand terabytes. photo site A name for the individual receptors that comprise an image sensor. In most image sensors each photo site only captures a single color value (typically red, green, or blue), with the other values calculated by extrapolation. While each photo site captures a value that is ultimately used to create a pixel in the final image, it is a bit of a misnomer to refer to a photo site as a pixel for image sensors that do not capture a full color value at each photo site for all pixels in the final image. Photoshop Document A file format used by Adobe Photoshop as the native format supporting the many imagerelated features available in Photoshop, including image layers, adjustment layers, layer masks, alpha channels, and more. This file format is generally referred to using the acronym PSD, and.psd is the default filename extension. picoliter One trillionth of a liter (sometimes described as one millionth of one millionth of a liter), often used as a measure of the ink droplet size for photo inkjet printers. pincushion distortion A type of lens distortion where horizontal or vertical lines in the scene are bent inward toward the center of the image. pinhole camera A simple camera that does not utilize a lens, instead making use of a very small (pinhole-sized) opening (aperture) in a light-proof box. Because of the extremely small aperture, the images captured with a pinhole camera exhibit virtually infinite depth of field. pixel A term derived from the words picture element, which describes the smallest individual unit in a digital photo. pixels per inch The number of pixels per linear inch on a display or as a value within an image file, used to calculate the overall output size for an image. For example, many photo inkjet printers render the image data at 360 ppi, so a 10-inch by 10-inch printed image would require an image that is 3,600 by 3,600 pixels to print with optimal quality. Note that simply changing the ppi resolution for an image does not automatically change the number of pixels in the photo. Generally speaking, the ppi resolution of an image is only applicable when sizing an 52

53 image to be printed. The ppi resolution of a display provides one indication of the overall potential quality of the display in terms of the ability to represent fine detail. See also dots per inch. plenoptic In the context of photography, a lens typically consisting of a large number of micro-lenses that enables a digital camera to capture not only the intensity and color of light but also the direction of that light. A plenoptic lens makes a variety of post-processing in software possible, such as the ability to refine depth of field after the capture. PNG An acronym for the portable network graphics file format. See also portable network graphics. polarizer See polarizing filter. polarizing filter A filter that can be placed in front of a lens, and which filters out light based on the angle of light rays reaching the camera. Such a filter can be used to reduce the appearance of reflections and haze, as well as to reduce the amount of light reaching the camera s image sensor for purposes of achieving a longer exposure. Portable Document Format A file format developed by Adobe that enables documents containing text and graphics to be described in an efficient way while preserving the overall layout and appearance across multiple operating system and hardware platforms. This file format is generally referred to using the acronym PDF, and.pdf is the default filename extension. Portable Network Graphics A bitmap-based image file format that utilizes lossless compression to reduce file size and supports transparency. Despite its advantages relative to the JPEG file format for online graphics, the PNG file format has not achieved the broad use that the JPEG file format has achieved. This file format is generally referred to using the acronym PNG (generally pronounced ping ), and.png is the default filename extension. portrait orientation An vertical orientation for a photo where the height is greater than the width. post-processing A term that is often used to describe work that is performed on a digital photo after it has been captured, most commonly in reference to work that changes the actual appearance of the photo. posterization A visible effect in an image caused by the loss of smooth gradations of tonal or color values 53

54 with an image. Often caused by strong adjustments, particularly with images being worked on at a low bit-depth, posterization generally appears as banding along gradations in a photo. ppi An acronym (though one that is generally not capitalized) for pixels per inch. See also pixels per inch. Preserve Details An interpolation algorithm introduced in Photoshop CC, and which provides improved detail and sharpness compared to other interpolation algorithms when enlarging an image. primary colors A minimal set of colors that can be used to produce all other colors. For example, in the RGB color space red, green, and blue light are blended together at varying intensities to produce a wide range of possible colors. See also additive primary colors and subtractive primary colors. prime lens A lens with a single fixed focal length. printer profile An ICC profile that describes the color behavior of a specific combination of printer, ink, and paper. Printer profiles are used to translate the source image data to the color gamut of the printer, in order to compensate for the behavior and limitations of the output conditions. profile See ICC profile. profile connection space The color space used by software as a reference when translating colors between different profiles. Color values are typically translated from the source color space into the profile connection space, and from there to the destination color space. The Lab color space is most often used as a PCS. profile mismatch A situation where the profile embedded in an image does not match the current working space profile for the software being used to open the image. profiling The process of creating an ICC profile that describes the color behavior of a particular device under specific conditions. For example, profiling a printer, ink, and paper combination involves measuring the output produced from known values in order to determine the behavior and limitations of that output combination. See also characterization. 54

55 program mode A exposure mode available on many cameras that employs fully automatic (or nearly so) calculation of exposure and exposure settings. progressive In the context of digital video or a digital display, a configuration whereby the overall image is created with each line drawn in sequence. This contrasts, for example, with an interlaced display, whereby two or more passes are used to draw the full image, with alternating lines of the image refreshed with each pass. See also interlaced. ProPhoto RGB An extremely large-gamut RGB color space developed by Eastman Kodak Company and available as a working RGB color space in a variety of software applications. The ProPhoto RGB color space is large enough to include all colors likely to occur in the real world, and in fact the range also includes imaginary colors that do not actually exist as visible colors. PSD An acronym for the Photoshop document file format. See also Photoshop Document. 55

56 Q quadtone An image mode in Photoshop that enables you to create images comprised of four base colors defined by the user. See also duotone and tritone. quick-release A term describing a system of camera mounts that enable the quick mounting and releasing of the camera system from a ball head or other support mechanism. A quick-release system typically employs a plate attached to the camera as well as a compatible quick-release mount on a ball head or other support. QuickTime A multimedia format developed by Apple providing a platform for the creation and playback of digital video, still images, interactive panoramic images, audio, and other digital information. 56

57 R RAID An acronym for redundant array of independent disks (or drives). See also redundant array of independent disks. RAM An acronym for random access memory. See also random access memory. random access memory A form of volatile memory used by computers and other devices as temporary storage for information being processed. raster image processor A hardware or software component that handles the job of converting computer data to printer data, often including color-management features and other capabilities that can improve the accuracy and quality of the final print. RAW A category of file formats that record the actual data gathered by the image sensor during a photographic exposure with little or no modification of that data. These RAW file formats are not actual image files, and must be converted to full pixel data by software designed for this purpose. RAW is often presented as all-caps as though it were an acronym even though it is not an acronym for consistency with other image file formats that are actual acronyms. RAW conversion The process of calculating the full-color pixel values for an image captured in a RAW file format. With most digital camera image sensors each pixel within the capture only has a single color value, such as either red, green, or blue for a typical RGB capture. In the RAW conversion process, the remaining values are calculated through a form of interpolation. For example, if a particular pixel only contains a red value, during the RAW conversion process the green and blue values will be calculated for that pixel, producing the actual RGB color for that pixel. RAW conversion is also referred to as RAW processing or demosaicing. See also demosaicing. RAW DNG A file in the Adobe Digital Negative (DNG) format that contains RAW capture data. See also digital negative. 57

58 RAW processing See RAW conversion. rear curtain synchronization A feature of many cameras that causes the flash to fire just before the shutter closes, rather than as soon as the shutter opens. This enables a more natural appearance when photographing moving subjects with a relatively slow shutter speed, since the motion blur will be captured before the flash illuminates the subject. reciprocity The inverse relationship between the intensity of light and duration of exposure to that light. In photography the intensity of light exposing the image sensor or film is controlled by the lens aperture, and the duration of exposure is controlled by the shutter speed. reciprocity failure A condition whereby the inverse relationship between intensity of light and duration of exposure to that light is no longer maintained. For example, under extremely dark lighting conditions the response of film (or an image sensor) will not be predicable based on behavior under bright lighting conditions. Thus, for example, the exposure time may need to be more than doubled even if the light has half the intensity. redundant array of independent disks A storage configuration, often referred to by the acronym RAID, whereby multiple hard drives are interconnected to produce an advantage of either performance or data redundancy (or both). reflective layer The layer in an optical disc that provide reflectivity for the laser used to read data from the disc. reflector A device employing a reflective surface (often with a color cast, such as gold, for imparting a color cast) that is used to reflect light from a source (such as the sun) to serve as supplemental light. For example, a reflector is often used when photographing people in order to soften shadows and equalize the lighting to match the background. refraction A phenomenon whereby light rays are bent upon passing through a lens or other medium. relative colorimetric One of the four ICC rendering intents for handling out-of-gamut colors when converting colors from a source to destination profile. Colors that are within the gamut of the destination profile are reproduced accurately. Colors that are outside the color gamut of the destination profile are shifted to the nearest reproducible color. White is mapped to the white of the destination space, with all colors adjusted based on that white point. 58

59 rendering intent A method for dealing with out-of-gamut colors when translating colors between two color space profiles. The four ICC rendering intents are absolute colorimetric, relative colorimetric, perceptual, and saturation. resampling The process of calculating the value of pixels during the process of resizing an image to change the total number of pixels in the image. Resampling is often referred to as interpolation. See also interpolation. resizing The process of increasing or decreasing the number of pixels in an image to produce a larger or smaller output size. Resizing is often referred to as interpolation. See also interpolation. resolution A measure of the amount or density of information in a digital photo. When referring to the amount of information, resolution is the total number of pixels (generally referred to in megapixels) or pixel dimensions (the number of pixels across by the number of pixels down, such as 1024x768). When referring to the density of information, resolution generally refers to the number of pixels per linear inch (in an image) or dots per inch (in a print). reverse engineering The process of determining how a particular piece of technology was implemented by studying that technology in detail. This often involves, for example, the disassembly of a technological device to determine how that device operates. In digital photography the term reverse engineering is often used to describe the process of determining how digital capture information is stored within a proprietary RAW capture format when documentation of that RAW format is not provided by the camera manufacturer. ring light A type of flash typically attached to the end of a lens (commonly a macro lens) and employing a diffuser that distributes the light from the flash evenly in a ring around the lens, providing soft and even light to the subject in front of the lens. RIP An acronym for raster image processor. See also raster image processor. RGB A color model based on the additive primary colors of red, green, and blue. This color model is used to represent colors based on how much light of each primary color would be required to produce a given color. 59

60 S SATA An acronym for Serial Advanced Technology Attachment. See also Serial Advanced Technology Attachment. saturation (1) The property of a color that describes its purity. With higher purity, a color will appear more vibrant, while with lower purity it will appear more dull (closer to gray). Saturation is one of the attributes in the HSB (hue, saturation, brightness) color model. See also chroma. (2) One of the four ICC rendering intents for handling out-of-gamut colors when converting colors from a source to destination profile. With the saturation rendering intent, highly saturated colors in the source space are mapped to highly saturated colors in the destination space, with possible changes in hue and lightness. scanner profile A profile that describes the color behavior of a scanner so the scanned images can be adjusted automatically to compensate for how the scanner interprets color information as well as the specific color gamut capabilities of the scanner. scanning back A type of digital camera back that captures a scene by scanning a single row or column image sensor across the image circle projected by the lens. A scanning back can capture images with higher detail and quality than traditional image sensors, but also requires a longer time for capturing the full image and is not well-suited to moving subjects. SCSI An acronym for Small Computer System Interface. See also Small Computer System Interface. scene-referred A term that refers to image data that reflects estimated values of what the original scene actually looked like in the real world. This can differ from image data that reflects the output capabilities of a monitor display or a printed result, or from the linear data captured by an image sensor in a digital camera. selection A definition of specific portions of an image in digital imaging software, typically defined as a percentage of inclusion in the selection for each individual pixel, so that pixels can be partially selected. A selection is commonly used to apply some form of adjustment that will only affect 60

61 specific pixels within the image. semi-gloss A surface (such as paper) that is glossy but without as much reflectance as more typical glossy surfaces. See also semi-gloss. sensor See image sensor. sepia A reddish-brown color, often applied as a tint or shading for a monochromatic photographic image. Also the ink or pigment, which was originally produced using the secretions of cuttlefish, which are marine mollusks similar to squid. Serial Advanced Technology Attachment An update to the original Advanced Technology Attachment (ATA) interface standard for connecting hard disk drives, offering higher data transfer speeds and simpler cable connections, among other benefits. shade (1) A particular color value, generally of a relatively dark and subdued value. Shades are traditionally created by blending a color, such as a pigment, with black. See also hue and tint. (2) A device for blocking light, such as to reduce the amount of light illuminating a subject or to prevent lens flare. See also lens shade. sharp A condition of relatively strong contrast along detail edges in a photo, resulting in an appearance of being in focus and with relatively strong detail edges. sharpen A process of improving the appearance of sharpness within a photo, often performed by software that applies an increase in contrast along existing contrast edges in a photo. sharpening artifacts Artifacts such as contrast halos along contrast edges in a photo caused by sharpening settings that are too strong for the image being processed. See also artifact. shutter speed The duration that the light projected through the lens is exposed to the image sensor to record a photographic image. A slow shutter speed (such as 1/2 second) can result in a blur effect if there is motion either in the scene or of the camera. A fast shutter speed (such as 1/500th of a second) can help freeze motion in a scene. 61

62 shutter speed priority mode A camera exposure mode where the photographer sets the desired shutter speed setting and the camera calculates the optimal lens aperture based on metering. The shutter speed priority mode is sometimes referred to time value mode since the photographer is setting the time that the shutter will remain open. silicon A non-metal chemical element that exhibits semiconducting properties and is frequently used in making electronic circuits and other components. single-lens reflex camera A camera that utilizes a mirror to allow the photographer to see the view through the lens using a viewfinder, so that the scene being photographed can be accurately previewed. The mirror moves out of the way when the photograph is taken so the light projected by the lens can be recorded by the film or image sensor. SLR An acronym for a single-lens reflex cameras. See also single-lens reflex camera. Small Computer System Interface An interface for connecting peripherals to computer systems, used primarily for connecting hard disk drives, but now largely replaced by newer interface options. SmartMedia A storage device format employing flash media for storage, and used for storing images with many digital cameras. The SmartMedia standard is owned by Toshiba. snapshot A term used to describe a photograph captured for generally casual purposes as opposed to artistic purposes. This term is also used to describe a saved history state for a photo, which enables the user to return to a particular condition for the photo while processing the image using software. soft box A lighting accessory that consists of a frame and diffusing material, which is placed over a light source to provide a softer light illuminating the subject to be photographed. soft proofing A feature of various imaging software applications that allows you to get a preview of what the image will look like when printed using a specific profile. software Programs that perform a variety of functions on a computer system by submitting instructions to the operating system, and often by taking input from the user. 62

63 solid state A term describing an electronic device that operates without the use of moving parts. solid state drive (SSD) A storage device that makes use of flash media for storage, enabling high transfer speeds, low power consumption, no moving parts, and other benefits. source profile The ICC profile that is being used to interpret colors in an image before the color information in that image is converted to a different profile. The profile being converted to is referred to as the destination profile. See also convert profile and destination profile. spectral curve A graphical representation of the wavelengths of the visible spectrum that comprise a specific color. spectrophotometer An instrument that measures the amount of light at each wavelength reflected or emitted by a color sample. This provides data for building an ICC profile. spot color An individual ink color used in offset printing. In one of the more common examples of offset printing, four spot colors are used (cyan, magenta, yellow, and black), each printed individually with a single print pass for each ink color. However, it is possible to use any color ink for each of the spot colors in the printing process. The term spot color is also often used to refer to an extra color ink that is used for an additional print pass beyond cyan, magenta, yellow, and black, to achieve a result that would not be possible with a normal CMYK output process. For example, a special metallic gold ink may be used to add special elements to a print job that otherwise makes use of the traditional CMYK set of inks. See also CMYK and offset printing. spot metering A metering mode whereby a small area (generally 1% to 5% of the field of view of the lens, for example) of a scene is evaluated for purposes of calculating proper exposure settings. srgb A working space profile with a color gamut originally designed to encompass the range of colors that could be displayed by a typical computer monitor. This makes srgb an appropriate general-use profile for use with images that will be displayed digitally (such as on a computer display or with a digital projector) rather than printed. SSD An acronym for solid state drive. See also solid state drive. standard illuminant An established standard that defines a specific illumination source used in a color-managed 63

64 workflow. Among other things, such a standard illuminant is used as the presumed light source that will be used to evaluate a printed image. See also D50 and D65. standard lens See normal lens. standard observer An established standard that defines specifications for a hypothetical observer representing typical human color vision, which helps to ensure consistent communication about color values in a color-managed workflow. strobe A term describing a light source that flashes a high-intensity light for a very brief period of time, frequently referred to as a flash. sublimation A change from one physical state without passing through an intermediate state, such as a solid being converted to a gas without passing through a liquid state. See also dye sublimation. subtractive primary colors The primary colors (cyan, magenta, and yellow) for reflected light (such as in a print). In theory all possible colors can be reproduced using these primary colors. The absence of all three colors in a print results in the color of the paper (ostensibly white) to appear, and in theory combining all three colors at their maximum produces black. In an actual printing environment black ink must also be added to produce as close to a true black as possible, and there are limits to how much ink can be placed in a given area of the print. Super Extended Graphics Array A standard display resolution with dimensions of 1280x1024 pixels, generally referred to by the acronym SXGA. SXGA An acronym for Super Extended Graphics Array. See also Super Extended Graphics Array. 64

65 T tagged image file format A standardized file format for saving images for a variety of purposes. The tagged image file format supports the inclusion of layers, layer masks, alpha channels, and other features, making it useful as a file format for saving complex layered images. This file format also supports compression (both lossless and lossy) to help reduce file sizes. target image A reference image, typically employing objects reflecting memory colors, that can be used to help evaluate results from a particular device. For example, the PhotoDisc, Inc. (PDI) target image is commonly used to evaluate the accuracy of monitor displays or printed images. See also memory colors. targeted adjustment A term describing an adjustment to the appearance of an image that only affects a specifically defined area of the image. tele-converter A supplemental lens element, sometimes referred to as a tele-extender, that provides additional magnification for an existing lens. For example, a 2X tele-converter can be attached between a lens and camera body to provide the effective field of view of a lens with double the actual focal length of the lens. tele-extender See tele-converter. telephoto A term describing a lens with a relatively long focal length, and thus a relatively narrow field of view. terabyte One trillion (1,000,000,000,000) bytes of information, generally used in the context of storage capacity or file sizes for a computer system. thermal inkjet An inkjet printer technology that utilizes heat to spray ink droplets onto paper. This is contrasted with the Micro Piezo technology that utilizes vibrations to spray ink droplets onto the paper. See also Micro Piezo. 65

66 through-the-lens metering A feature of cameras that makes use of the image being projected by the lens as the basis of exposure calculations, helping to ensure accurate metering since the actual light that will be captured is being used as the basis of exposure. thumb drive A general term for small flash media storage devices, typically those that connect via USB or other interface directly to a computer, and providing for portable storage. Thunderbolt An interface for connecting peripheral devices to a computer, developed by Intel and initially launched with collaboration from Apple. The Thunderbolt interface can be used as a data connection for displays, storage devices, and other peripherals, and offers a maximum data throughput rate of 20 gigabits per second (Gbps). TIF A shortened version of the TIFF acronym for the tagged image file format. This shortened acronym is commonly used as a filename extension, since older operating systems often limited filename extensions to three characters. See also tagged image file format. TIFF An acronym for tagged image file format. See also Tagged Image File Format. time-lapse A video comprised of a series of still images captured at a specific interval, which compresses time relative to the subject photographed. As an example, if a series of images are captured at an interval of one frame each second and then assembled into a time-lapse video at 30 frames per second, the video will present an accelerated view of time where one second in the video represents 30 seconds of time from the original scene. time value mode Another term for shutter speed priority mode. See also shutter speed priority mode. tint A particular color value, generally of a relatively bright and subdued value. Tints are traditionally created by blending a color, such as a pigment, with white. See also hue and shade. tone-mapping The process of recalculating tonal values to fit within a specified range. For example, with high dynamic range (HDR) imaging, you can produce a set of data that exceeds the ability of a monitor display to project the full range of tonal values, or that exceeds the ability of a specific printer, ink, and paper combination to reproduce that full tonal range. Through tone-mapping, this extended range of tonal values is compressed into a smaller range. With this process, an image that contains an extremely large range of tonal values can thus retain considerable detail 66

67 while still being able to be presented with good fidelity on monitor displays and through printed output. trademark A form of intellectual property protection that protects a name, symbol, or mark representing a particular product or company. tripod A camera support that consists of a three legs and a mounting point for a camera, providing a stable platform that can ensure sharp due to the lack of camera movement. tritone An image mode in Photoshop that enables you to create images comprised of three base colors defined by the user. See also duotone and quadtone. TTL An acronym for through-the-lens metering. See also through-the-lens metering. TV mode An acronym for time value mode, also referred to as shutter speed priority mode. See also shutter speed priority mode. 67

68 U UDMA An acronym for Ultra Direct Memory Access. See also Ultra Direct Memory Access. Ultra Direct Memory Access A data transfer protocol that transfers data directly from storage to the computer s random access memory, enabling high-speed data transfers of up to 33.3 MB per second. Ultra Extended Graphics Array A standard display resolution with dimensions of 1600x1200 pixels, often referred to by the acronym UXGA. ultraviolet filter A filter (often referred to as a UV filter) placed on the front of a lens in order to block ultraviolet (UV) light from entering the lens. The use of an ultraviolet filter can reduce the appearance of haze for images captured outdoors. umbrella A device that resembles an umbrella used for protection from rain, but which is specially designed to reflect or diffuse a light source in order to provide softer light to illuminate a subject. Universal Serial Bus An industry standard interface for connecting peripheral devices to a computer system. The original USB 1.0 interface supported speeds of up to 12 megabits per second (Mbps). USB 2.0 supports speeds of up to 480 megabits per second (60 megabytes per second), and USB 3.0 supports speeds of up to 5 gigabits per second (625 megabytes per second). USB An acronym for Universal Serial Bus. See also Universal Serial Bus. UV filter See ultraviolet filter. UXGA An acronym for Ultra Extended Graphics Array. See also Ultra Extended Graphics Array. 68

69 V Vibrance Generally regarded as being synonymous with the term saturation, Vibrance is an adjustment available in various software applications such as Adobe Photoshop, Adobe Photoshop Lightroom, and Adobe Camera Raw. This adjustment provides a more balanced increase in saturation in the image, protecting skin tones in particular from becoming too saturated. vector graphic A method of describing an image through the use of points, lines, and curves, where individual pixel values do not need to be recorded. A vector graphic yields a smaller file size than a bitmap image, and that can be infinitely resized while retaining image quality. VGA An acronym for Video Graphics Array. See also Video Graphics Array. video card See display adapter. Video Graphics Array A hardware standard for computer video displays originally released by IBM in Generally referred to by the acronym VGA, this standard has also come to refer to the 15-pin connector used for VGA displays, as well as the 640x480 pixel resolution utilized by VGA displays. video lookup table The lookup table (LUT) on a display adapter (also referred to as a video card) that contains the color signal values used to produce specific colors for the display. This data is updated by the operating system and monitor calibration tools to produce a more accurate display. video memory The memory that is used by the display adapter when processing data used to produce a display, such as on a monitor. video RAM See video memory. viewing booth An illumination device (such as a lamp) that produces light matching one of the standard illuminants (typically D50) so that printed colors can be evaluated based on established color 69

70 management standards. While evaluating colors utilizing a viewing booth does not necessarily simulate the actual conditions under which a print may ultimately be displayed, doing so is helpful in terms of evaluating the accuracy of a color-managed workflow. See also D50 and standard illuminant. vignette A darkening of the edges of a photographic image, often caused by light falloff near the edges that can result from the extreme angles of light projected by a wide-angle lens. Computer software allows you to compensate for the appearance of vignetting, and also to add a vignette to an image that did not exhibit such an effect in the original capture. visible light See visible spectrum. visible spectrum The portion of the electromagnetic spectrum that produces a response in the human visual system, encompassing wavelengths from about 380 nanometers to about 780 nanometers. See also light. 70

71 W white The brightest color available for a digital image, generally described as having a brightness of 100% or RGB values of R256, G256, B256 (with an 8-bit per channel image). While the concept of white seems like an absolute, in the context of a digital image the true appearance of white depends upon the device producing the image. For example, when printing the color of the paper determines the maximum white value for a printed image, and the maximum light intensity a monitor or digital projector can produce determines the limit for a maximum white value. white balance An adjustment that compensates for the color quality of the light illuminating a scene. A white balance adjustment can be used to ensure that objects appear with their natural color, but can also be used to ensure a more pleasing color that isn t necessarily completely accurate relative to what was observed in the scene. white balance preset A preset offered by a digital camera that allows you to apply a color compensation to the image based on the color temperature of the light source illuminating the scene. Common white balance presets include tungsten, fluorescent, flash, daylight, cloudy, and shade, among others. white point adaptation An aspect of the human visual system that causes an automatic compensation for color appearance caused by the influence of color in the illumination source, based on a perceived white in the scene. For example, if a print with a paper-white border is displayed under a light source with a relatively yellow color tint, the human visual system will compensate for the yellow seen in the area closest to white. This is what allows people to recognize the actual color of objects even if those objects are illuminated by light with a strong color element. Wi-Fi A term describing a wireless local area network for the purpose of enabling computers to share resources or to connect to the Internet. The term Wi-Fi is a trademark of the Wi-Fi Alliance. wide-angle A general term for lenses with a relatively short focal length and therefore relatively wide angle of view. In common practice lenses with focal lengths shorter than about 50mm for the 35mm camera format (or those with a field of view of 60-degrees or greater) are typically referred to as wide-angle lenses. 71

72 widescreen A general term for digital displays or resolutions that have a relatively wide aspect ratio, typically defined as an aspect ratio wider than a 4:3 ratio of width to height. Widescreen Extended Graphics Array A set of display resolutions that translate the standard XGA resolution (1024x768) to widescreen displays. WXGA resolutions include pixel dimensions of 1280x720, 1280x768, 1280x800, 1360x768, and 1366x768. Widescreen Ultra Extended Graphics Array A standard widescreen display resolution with dimensions of 1920x1200 pixels, often referred to by the acronym WUXGA. Windows Media Video A video format developed by Microsoft, featuring compression technology to reduce file size. wireless network A local area network that utilizes wireless technology to enable computers to share resources or connect to the Internet without the need to utilize a physical data connection. WMV An acronym for Windows Media Video. See also Windows Media Video. working space profile A profile that determines the range of colors available for a given image when working with that image using digital imaging software. Such a profile provides a generic range of colors that strike a balance among the wide range of color gamuts for digital displays such as monitors and digital projectors as well as many printers. See also Adobe RGB, ProPhoto RGB, srgb, and embedded profile. World Wide Web A widely available system of specially-formatted documents available via the Internet. See also Internet. WUXGA An acronym for Widescreen Ultra Extended Graphics Array. See also Widescreen Ultra Extended Graphics Array. WXGA An acronym for Widescreen Extended Graphics Array. See also Widescreen Extended Graphics Array. 72

73 X XGA An acronym for Extended Graphics Array. See also Extended Graphics Array. x-ray A range of electromagnetic radiation with high energy and short wavelengths, falling below the range of energy of visible light. 73

74 Z Zip Drive A data storage system created by Iomega in 1994 that initially offered storage capacity of 100MB per disk, with later updates offering 250MB and 750MB capacities. zoom lens A lens with a mechanism enabling the effective focal length to be adjusted within a specific range, enabling the field of view of the lens to be adjusted accordingly. 74

75 The Digital Photographer s Glossary by Tim Grey About the Author Tim Grey is regarded as one of the top educators in digital photography and imaging, offering clear guidance on complex subjects through his writing and speaking. He has authored more than a dozen books and hundreds of magazine articles on digital imaging for photographers, and has produced dozens of video training titles on a wide variety of subjects. He publishes the Ask Tim Grey newsletter, as well as Pixology electronic magazine. Tim teaches through workshops, seminars, and appearances at major events around the world. For more information: ISBN: Version 2.0 Published November 6, 2013 Copyright 2013 by Tim Grey. Published by: Tim Grey 328 8th Avenue #132 New York, NY tim@timgrey.com The author has attempted throughout this book to distinguish proprietary trademarks from descriptive terms by following the capitalization style used by the manufacturer and marking those marks as either a trademark or registered trademark. All trademarks and registered trademarks included in this book are the property of their respective owners. The author has made best efforts to prepare this book, but makes no representation or warranties of any kind with regard to the completeness or accuracy of the contents herein and accept no liability of any kind including but not limited to performance, merchantability, fitness for any particular purpose, or any losses or damages of any kind caused or alleged to be caused directly or indirectly from this book.

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