Instructors Notes Slide actions are described in these notes as well as additional comments and information: <C> = Click on Slide Advance button. Actions follow the symbol and are enclosed in parentheses. Improving our Digital Photographs Session 1 Photography is both a bit of a science and a bit of an art. <C> (Red text on glass ball appears. Black text appears after 1 second) Read new text as it appears. The science side is understanding what we thought we saw and capturing that image. The art side is recognizing the feeling you want the photo to evoke and capturing that image. Notes: This photo was taken at the Chihouly Art Glass exhibit at the Dallas Arboretum in October of 2012. The flowers provide a visual base to the photo and provide scale for the glass balls. (No, they aren t marbles. They re that big!) Without the text, the photo is not well balanced. The large ball is too near the edge and (sort of like gravity with a teeter-totter) the eye us drawn to the heavier area. Additionally, the large ball falls on the Rule of Thirds line. This draws the eye to it also, providing a great backdrop for the important text. The dark leaves in the upper right add visual weight (in the form of a negative space) to the left side. Placing the white text there helps balance the overall image. 1
2
I group photos into 1 of 4 categories, depending on what I expect to capture with the image. The category allows me to concentrate on the aspects important for that type of photo. The first aspect to consider is the camera settings like resolution. In my case, I have plenty of memory in my camera and download images regularly. Therefore I set my camera for the highest resolution and image quality. That results in the largest file size with the fewest images possible available to be stored. However, many people using cell phone and small cameras keep all photos on them to show. Using less resolution and image quality will make much smaller files size and allow many more images to be stored, and the quality loss will not be noticeable on the device screen. In this case, I recommend switching to better settings if you think that some of the next images might be downloaded. In most cases, the automatic settings for focusing, color balance, and exposure are fine. However, for what I call Forensic photos, we want to capture details accurately and we might need to control the camera s color balance, exposure, and even focus and f-stop. Also for Forensic photos, to accurately capture the image, we want to pay close attention to our perspective, the location and type of the light source, and the composition of the photo. For Photos That Tell a Story, we are trying to capture the feelings we felt when we first saw the scene. We want to highlight the subject while looking for ways to minimize any distractions. This is where Art Theory will be useful. The key to these photos is to be very observant and use your imagination to capture a great image. As these image have a good chance they will be shared as prints or on a PC, using higher resolution and quality is probably best. 3
Most of the photos that we take are Record shots capturing a moment in time to remind us of a happy time whenever we later see the photo. Forensic accuracy is generally not required a little color shift, a little error in visual perspective, or even being a little too bright or dark doesn t ruin the image for us (as long as the problems are not too distracting). Using medium resolution and JPEG quality give a small file size, allowing us to fit more images on our camera or phone. However, as the other types of photos are best taken with the highest setting, if memory space allows, it would be easier to leave the highest setting rather than remembering to reset things later. Generally, the full automatic settings for focus, aperture, shutter speed, color balance, and ISO will be fine for Record shots. This minimizes the technical thinking required, allowing us to concentrate on the artistry in the image. Look carefully and move around to remove any distractions and consider how much of the area to include to set the lens zoom. The final category is Artistic photos. We might want to capture the beauty of the sunlight on and through a flower or the emotion of an event; we might use it as the desktop background on our PC or make a print for the hallway wall. The image of the mesas in the upper right was taken to use to make a quilt pattern, edited on my PC to create the line drawing below it. High resolution and JPEG quality are more important than a small file size. Accurate colors are very important, so we might need to play with the camera color balance setting. Generally, we want a very simple image so nothing distracts from the subject or emotion. The depth of field, point of focus, angle of view, and even shutter speed must be considered. Or am I too technical to think artistically? 4
We will begin with a few minutes on how a camera works, how our vision works, and how those two things interact with each other. But first, a few memories of cameras from my past: Upper left photo left to right: My parent s old camera oh do I remember facing the sun, trying not to squint. Two cameras that I collected My first Pocket 110 camera with an electronic flash I added. I had a 2X Tele-converter to clip over the lens. I kept one Flashcube for emergencies and found I could use the flash extender with a used Flashcube to get a slower shutter speed for lower light conditions. Upper right photo: Some of the filters I still have from my SLR film camera days. Lower photo right to left: My Nikon Pronea S a SLR camera that used the same lenses as my big SLRs, but uses the APS film (about the size of the old 110 film, but with a recording strip to store camera settings to improved developing and printing). The memory card from my first digital camera. Remember when 128 MB was a LOT of memory? My second digital camera Canon A70. I also got an attachment that allowed filters to be screwed directly to the camera and I got a 3X Tele-converter that screwed on also. My first SLR film camera Nikormat FT3 and electronic flash for that camera ( middle rear). 5
Ф 1 Ф 2 Ф 1 Apparent Path Actual Path A Little Theory Light radiates from a source in waves, like ripples on a pond when you toss in a rock. The direction of travel is perpendicular to the wave crests. When light waves cross from air to any material (water, glass, etc.), the wave speed slows down. The slower wave speed results in the wave crests getting closer together inside the material as shown in the figure at the left. The offset in the optical path as our brain assumes the light ray is straight results in an optical illusion. The basic principles of how a lens creates an image can be demonstrated from the discussion above. An image is formed when light rays are forced to converge (focus), as shown on the slide. The lens provides this effect. The figure at the left shows a simplified diagram of the very top a lens. Invert this for the bottom half, and you see the basics. (Actually, a lens is a smooth curve rather than flat as shown in this example.) The distance from the lens to the image increases as the object is closer to the lens. Object Image Object Object Object 6
The camera lens has a sheet with a variable sized opening between the lens and the sensor. The iris in our eyes opens more in lower light (to let more light in) and closes more in brighter light (to block some light to prevent overloading the retina). The camera iris is often used for the same purpose. However, the diameter of the iris also controls how much of an area (in front of and behind the point of focus) is in good focus. A large diameter iris (lets in more light in lower light situations, but) gives only a small region of good focus around the point of focus. A small diameter iris (blocks more light in brighter light situations, but) results in a large region of good focus around the point of focus. Areas beyond this region of good focus range from nearly in focus to completely blurred. If the background is distracting, choosing a large iris (low f-stop number) will reduce the Depth of Field, forcing the distracting background out of focus. 7
The camera has a curtain assembly (shutter) that can open and close very fast and stay open as short or long as needed. A fast shutter speed helps freeze motion and reduce blur due to camera shake, but requires a bright scene to get enough light to the sensor while the shutter is open for a good exposure. The camera ISO setting controls the sensor sensitivity to light like ASA100 and ASA400 speed film. A high ISO setting allows a lower light scene to be photographed with a faster shutter speed and/or smaller iris (more depth of field), but can result in a grainy image (like ASA400 speed film). A low ISO setting requires a bright scene or slow shutter speed for a correct exposure, but provides a grain-free image. A very fast shutter speed is needed to try to capture the image of a hummingbird. In the shade of the Colorado forest using Automatic settings, the camera chose a slow shutter speed, resulting in a blurred image. To truly capture the wings of a hummingbird requires a shutter speed even faster than my camera allowed. Professionals usually use a very fast electronic flash unit. 8
The brightness of the recorded image is determined by these 3 factors: f-stop, Shutter Speed, and ISO setting. These controls interact so that increasing one while decreasing another can result in the same exposure but different Depth of Field and Shutter Speed. Cameras have preset shooting modes for certain situations. The Sports Mode uses a fast shutter speed, usually requiring a larger Iris (low f-stop number), resulting in a shallower Depth of Field. Portrait Mode uses a shallow Depth of Field to highlight the face and alters the 9
Most cameras have a menu options controlling Image Resolution and JPEG Quality. Using lower settings will reduce file size considerably at a tradeoff of a more fuzzy image. Neither the visible distortion nor the file size reduction is really linear, so it is a bit of a trial and error to find an acceptable tradeoff between small files and visible distortion. Unless the number of pictures that can be stored is a problem, I suggest using the highest quality. Resolution is the number of Picture Element (Pixels or dots) per square inch - the graininess of the image. Higher Resolution images can be enlarged more than lower ones and still look good. In the top row of photos, the low resolution image is acceptable at low magnification. I took the same photo at high, medium, and low resolution. Notice the image quality difference as the small area is enlarged. What if you found something of interest (perhaps a butterfly the size of one of the leaves) in the image and you wanted to enlarge that area? You would want to have the high resolution image to work with. This is also true in editing images. If you save an image in low resolution (for a smaller file size) and then increase the image to a higher resolution, the image will be fuzzy (and the file will not be as large as the original. This fuzziness will also show up if you start with a taken photo with a low resolution and increase the resolution with a photo editor. If possible, always take photos at the highest resolution. And Always save the original image file somewhere and work on a copy of it. JPEG Quality is a figure that represents the amount of file size compression used (100% = no compression = large file size; 10% = lots of compression = very small file size) Lower JPEG Quality artifacts show up as brighter and darker fringing (sort of like a target) around areas with a lot of contrast difference (bright to dark transitions) and blockiness in areas where colors slowly change. 10
In many respects, a camera simulates our own vision system. After all, the camera is trying to capture the image that we think we see. Both our vision system and a camera consists of: Fixed lens (element to do most of the focusing) and an adjustable lens to fine tune the image Sensor to capture the image and transfer it to memory for processing Adjustable aperture that opens and closes some to control how much light reaches the sensor A camera sensor has light receptors evenly spaced across the field of view. The light receptors on the retina in our eye are very densely packed in the very center. This HD Spot (as I call it) allows us to concentrate our attention in a small detail area and still pay reasonable attention elsewhere in the field of view Your brain automatically commands your eyes to center your vision on whatever it decides to concentrate upon. That area is seen with much more detail than the rest of the field of view. This visual separation can block us from noticing elements of the image that can be distracting to a different viewer. You need to be aware of the effect of this HD Spot and look around the frame for distractions after you identify the subject. It sounds obvious to note, but we have 2 eyes and (most of) our cameras only have 1 eye. Our brain uses the angle between the lines of sights of our eyes as they focus on an object to estimate the distance to that object depth perception. This also provides us with a degree of visual separation between the subject and the rest of the scene that might not be captured by the camera. 11
Our vision system focuses on the object in our HD Spot. A camera s autofocus feature will focus on object that are in one or more of the fixed areas around the frame. On many cameras, using menus, we can select which spot(s) to use. Or on some cameras, we can manually focus it ourselves. Neither of these options are convenient or fast to accomplish. It will take some forethought to set up the shot. Cameras have a similar automatic exposure system. The sensor (and internal computer) can open or close more the iris, open the shutter longer or shorter, or adjust the sensor sensitivity. The primary difference is that (using menus or controls) we can intentionally overexpose or underexpose the image. The pupils of our eyes automatically open or close more to get enough light to the retina without letting in too much and causing damage. In dim light, the pupil opens up more to let in more light. As we noted earlier. The larger pupil has less depth of field. It is often difficult to find an object as we scan around a darkened room. In this case, we usually squint our eyes. This smaller effective opening increases our depth of field. We are trading off a little less light for more depth of field. Besides the pupil opening and closing, the fluid in our eyes darkens in bright light and clears again in low light. This process takes a few moments, causing eyestrain as we enter a bright area. Also, when we enter a dark area, we can t see much until the fluid clears again. 12
Both the sensors in our eyes (called Cones on the retina) and in a camera are made of individual light sensors; and these sensors come as red, green, and blue receivers. Each sensor is sensitive to a range of colors. We have more green sensors than the red and blue ones. This allows us to see more details in greens (leaves, grass, etc.). Cameras have 2 green sensors for each red and blue in a set of 4. Some women have 4 color sensor types 2 different green sensors. They can recognize more detail in greens that the rest of us; and also images on TVs and PCs appear less realistic to them than the rest of us. (They are used to more green detail than the 1 green can create.) Our color sensors do not work well in very low light. We have a fourth type of sensor (call Rods) that only works in low light. They are most sensitive to the yellow color of moonlight and are more dense along the edge of our field of view. Our brain uses certain color clues to adjust the colors that (we think) we see to reduce distractions as we move between light sources. Outdoors in the sun, a white ball looks white; in the shade, it looks slightly blue; indoors under incandescent light, it looks slightly yellow; and under fluorescents, it appears slightly green. However we do not see those color changes. Without Color Balance Correction, a camera will indeed capture those color differences. Cameras have a variety of color correction settings. This color correction in our brain is just one of many Image Processing shortcuts our brain employs regularly. These shortcuts allow us to recognize the image and take any actions required very fast ( fight or flight ). Other shortcuts range from recognizing what shape or perspective that is there (and making us believe that is what we see) to noting only (what it decides are) the most important aspects of the image (and having us ignore the details ). The camera will capture those details that our brain ignored. 13
Signs are generally intended to inform or warn us. All of these photos except the bee were taken on a fall vacation touring the national parks in Colorado, Utah, Arizona, and New Mexico a few years ago. The bee was on a tree in my front yard. We are going to look at a series of photos that represent what we saw compared to the image we took. On a computer, we use the term WYSIWYG (wiz ee wig) = What You See Is What You Get. 14
Optical Illusions are based on the Image Processing shortcuts our brain employs. So this is a good place for us to begin our quest to understand what we thought we saw and capture that image. 15
When I looked at the Iris and the 2 quilts, at the time they appeared to me like the top photos. The sun was out in a blue sky with only a couple of clouds for both of the top photos. I took the photos below them a few minutes later as the sun was hid behind a small, dark cloud. Notice the difference in the color balance. No difference was obvious at the time. In the top photos, direct yellow sunlight as well as blue skylight illuminated the area and the yellow and blue balanced to provide white light. In the bottom photos, the small, dark cloud blocked the direct yellow sunlight and the area was illuminated by only the blue skylight. The blue light canceled the yellows in the flower and the quilt. The white garage door (behind the quilts) has a blue tint. Even the green leaves (behind the flowers) have a blue-green tint. This blue-yellow shift (sun vs. shade) is easily corrected with most photo editing programs. (Of course, it is a lot easier when you can hold the laptop next to the garage door to match the color.) 16
These photos all have exposure problems, and represent a very common issue for photographers. In the left photos, most of the area is white snow and sky. The camera meter will either: Try to make the average brightness of the scene middle grey (like grey shirt cardboard), and the imaged ends up too dark. Most older cameras use the Average Metering. Or try to make the average of the darkest and whitest areas average to middle grey. The image will still be too dark, but not as much so. Most newer cameras use the Matrix Metering. The quilt photos were all taken in Fully Automatic mode with Flash. In the 2 quilt photos in the center, the black quilt caused the camera to brighten the image while the white quilt caused the camera to darken image. Note the difference in brightness of the backdrop curtains in the bottom pair of photos. The quilt photos on the right are a simple mistake. In the bottom photo, my thumb was covering the flash and the camera didn t have enough light. 17
These photos represent our excitement to capture an image causing us to miss some distractions. In the top left photo, I rotated the image slightly and covered the light pole with a piece of sky (to simulate what I saw actually, what I didn t see). In the top right photo, I copied areas of the grass to cover the car and street that my student missed. 18
Another shortcut our brain takes is with perspective. The part farther away appears smaller. When you look at a quilt, your brain knows it is rectangular, so it ignores the taper in the bottom photo. Unless you force yourself to compare the quilt edges with the camera frame, you don t notice that you are off center. In the right photos, you tend to ignore the perspective issue caused by fact that the building roof angles back and away to the left. The most obvious choice is to level the roof (bottom photo) rather than making the windmill vertical (top photo). 19
There are times that Fully Automatic needs a little help. In the forest, the shade forced a slow shutter speed. (I might question my camera s design here. I feel that it should have increased the ISO some so the shutter speed wouldn t be so slow.) Even though I wanted to stay as Automatic as possible, I increased the ISO to the highest setting possible while I chose a low f-stop number (large aperture with a small Depth of Field) so that the shutter speed would be the highest possible. If you want to freeze a hummingbird s wings in flight, it takes a shutter speed faster than almost any camera made. The bright light on the redbud tree forced a high f-stop number (small aperture with a large Depth of Field), resulting in the background becoming a distraction. Instead of forcing a low f-stop number to minimize the background, I could have put Neutral Density filters (dark glass) in front of the lens to force a high f-stop number. 20
The left pairs of photos are related to the use of the camera flash. A student brought me the bottom photo, asking where the shadow came from. The location of the flash relative to the lens on the camera. (This will be explained later.) Obviously you won t see the location of any flash shadows before the shot, but you can predict them and try to hide them. The close-up of the quilting shows the different effect that side light provides to show texture. The front flash shot shows no texture. (This will also be explained later.) Think about what you might do with the photo before you take it. Common photo print sizes are narrower than most cameras, so the left and/or right sides get cropped. In this case, you shouldn t zoom in so close to allow room to crop for the print. Wide-screen displays are wider than most cameras, so the top and/or bottom gets cropped rather than the left and/or right. 21
Autofocus can sometimes be a headache. The camera has fixed locations around the image where it will focus. Without a manual focus capability, it can be like a game of cat and mouse to get the image you want. This camera had no manual focus capability. I wasn t acquainted enough to search through the menus to find how to select only a single focus location around the image. So I tried the press the shutter halfway down, recompose the image, and press the rest of the way down approach. It was a new camera and a very fine difference between halfway down and fully down requiring a lot more practice than I had. So I got about 10 photos focused on the background for each photo focused on the flower of interest. (What a pain!) 22
Light sources come in many colors and tints. Under a blue sky in the sun, the colors are true. Under an overcast sky, the colors are also true. Under a blue sky in the shade, the colors are bluish. Under an incandescent light, the colors are yellowish. Under a fluorescent light, the colors are greenish. 23
The light leaving the sun is white it contains equal amounts of all colors. When reaches the earth s atmosphere, the sunlight strikes ozone atoms in the upper levels. Some of that sunlight is reflected off the atoms and bounces around the sky. Due to the size of the ozone atoms, mostly blue light is affected. We see the blue light bouncing around an therefore the sky looks blue. In photos from the Moon and Mars, the sky is black (and stars are even visible) due to the lack of atmosphere to bounce light around. When blue is removed from white light, the remaining light appears yellow. Therefore, direct sunlight looks yellow. So, objects illuminated by both direct sunlight and skylight will photograph with true (or almost true) colors. Shaded objects are missing the direct yellow sunlight and will photograph with a bluish tint. This is demonstrated in the photos of the goose. A shaded area of the tile was selected (left). I brightened that area to the same level as the rest of the tile (center), showing the bluish tint. I added yellow (right), showing the bluish tint is gone. The bottom example shows a similar process with a flash photo. The shadow created by the location of the flash relative to the witch s hat, is selected (left) and brightened to match the rest of the backdrop (center). Notice the yellow tint. With the shadow area created by the hat blocking the flash, that area was illuminated by the ambient room incandescent (yellowish) light. These color shifts will be captured in our photos. Most can be corrected with Photo Editing software, if necessary. Cameras have a variety of color correction selections available in the White Balance settings. 24
Color issues like on the last slide are, as noted, easily fixed on the PC or with the camera s settings. However, all too often, the various areas of the scene are illuminated by different light sources. These are much more difficult to fix, and generally some tradeoffs will have to be made. The drawings at the bottom represent the light spectrum for the various sources. (The background color shown for each source is an exaggeration of the actual color.) In the top row of quilt photos, the camera flash illuminated the quilt and backdrop, but the ambient room lights illuminated the ceiling. You can see some lights with a bluish tint probably quartz, some with a yellowish tint incandescent, and some with a greenish tint fluorescent. The camera flash provided a good color representation for the quilts. These images were cropped down to show just the quilts for presentation. The photo in the center has a section in full sun (too bright in this exposure), part sun (brightness about right and fair color), part shade (brightness about right but slightly bluish), and deep shade (dark, of course, but quite bluish). There is not (simple) way to correct the problems. Using fill flash (flash set at less than full strength, used to provide a little light into the shaded areas) or using a large white or foil reflector to add sunlight to the shaded areas are perhaps the best way to handle a situation like this if you want to go to the trouble. The photo in the lower left shows the color shift among the same type of trees up close and in the distance. The trees on the hillside in the distance have a definite bluish/violet tint as compared to the foreground tree. (Think purple mountain s majesty.) Light that comes from the distant trees bounces off of the atmosphere between there and here. While sunlight reflects off ozone atoms, making the blue sky. The atmosphere down here affects the purples and blues mostly. 25
The Killdeer image is a digital photo of a 8 x10 print. I laid the print on the living room floor, under the incandescent lights, and took the left digital photo. The original on the floor looked normal at the time. I downloaded the image and used a photo editor to correct the yellow tint. The editor told me to click on a gray area and it would correct everything. I had nothing gray so I clicked on the white rings around the collar. True gray has equal amounts of red, blue, and green. The editor looks at those values and alters the entire image to make those colors equal on the selected spot. Both black and white are grays. White has almost 100% of each color while black has almost 0% of each color. If the chosen spot was too white, the editor would have had more problems. A friend had taken the quilt picture at a Quilt Show (under fluorescent lights without flash) and was disappointed when she saw the color problems, primarily the lavender. She asked me if I could fix it. I had her give me a small piece of leftover lavender material. On close inspection, the whites looked fine, the face looked fine, and the colors in the needlework squares looked fine. Only the lavender off. (That is a common problem under fluorescent lights.) All attempts to correct the overall color balance resulted in problems in the whites and skin tones. Using my photo editor, I could tell it to choose all spots that were that particular (incorrect) lavender color and leave all the other spots alone. I then adjusted the red-green-blue balance for that color until it was correct. Remember, the problems were not obvious to the human eye at the time. Yes, if you looked at the image on the camera display, you would probably see the problems if you could enlarge it enough. 26
The angles involved in a photo wide angle to telephoto, distance to subject, etc. have a huge impact on the captured image. Unlike color balance, these are things that you can see before you take the photo. 27
Earlier, I noted that the perspective issues of not being square on to the subject are most often image processed to correct what we see. After all, we know that quilts are rectangular, so our brain ignores the tapering. If we concentrate, perhaps lining the edge of the quilt with the edge of the frame of the viewfinder, we will see that it tapers and isn t square. If we are off left, the top and bottom taper down to the right and vice versa for off right. If we are below center, the left and right taper down to the top and vice versa for above center. I am not saying to take every photo square on. However, when taking a Forensic Photo, you do probably want to be square on. I took the photo of the Columbine in front of the waterfall years ago with my first digital camera a point and shoot where the viewfinder was separate from the regular lens and sensor. Even the display didn t show the image after taking the photo. I lined the Columbine up in front of the dark spot to the left of the waterfall. But, the distance between the viewfinder and regular lens taken in conjunction with the Columbine being very close, led to the perspective error. I ended up with the right image. The left image was created by copying the flower and sections of the waterfall edge separately and carefully pasting them into the areas that I wanted them. The flower photos across the bottom show how different angles can change the photo. The translucence of the flower petals against the blue sky background provides good colors to affect our feelings. The tree branch background provides a sense of depth and presence. The head on rose photo has too much glare as well as shadow with no sense of depth. Either of the side views (the same rose cluster, by the way) avoid the contrast problems and provides a sense of depth and presence. 28
We saw these witch doll photos earlier. Here is where the flash shadow came from. In the landscape mode, the flash is above the lens. Shadows are formed below and behind objects. In this example, the only place for shadows to be seen are below the rim of the hat. In portrait mode, the camera is rotated on its side and the flash is beside the lens. Shadows are formed on the other side and behind objects. In this mode, shadows can be seen all along the opposite side of the doll. The front lighting from a camera flash is good for color rendition but it has several problems: It can hide any texture on the surface. It can glare off reflective surfaces. Red-eye is a form of glare off the blood veins in our eyes. Texture, like the puffy quilting, is much more visible when side lighted. In this case, a sky light in the ceiling above and to the left of the quilt provided the side light. This day had a clear blue sky, so the Note that the top-left of the little ghosts are bright and the bottom right are shadowed. If you don t have a skylight, a true color work lamp can be used. Finally, I included the full image (bottom right) to show how much detail can be seen, even from many feet away. The enlargement (side light) was cropped from this photo. Why do we get so close when we want to capture detail? 29
When taking a photo, most of us stand in one location and use the zoom lens to crop down to the area that we want. On this slide and the next, we will learn a few things about that habit. In each of these sets of photos, I stood in one location as I zoomed for the photos. The top left photo is with the lens at about the normal position and the top right photo is with the lens in the telephoto position. The bottom left photo is with the lens in the wide angle position and the bottom right photo is with the lens at about the normal position again. The center images are the areas noted by the yellow rectangle enlarged. Notice that when the center images are compared to the right images, that very little difference can be seen. Staying in the same location and using a zoom lens is (almost) the same as cropping and enlarging the image on a PC. The only real difference is in the number of pixels left. The center images above have considerably less resolution than the right images. But unless you plan to make a very large print, in all likelihood you won t see the difference. Many cell phone and tablet cameras and some less expensive point and shoot cameras do not have an optical zoom where the zooming is accomplished by moving some of the lens elements. These camera use Digital Zoom. (Some cameras have both, but each with limited range.) Optical Zoom uses all of the sensor area, maintaining full resolution. Digital Zoom uses a smaller area of the sensor when zoomed. This is the same as I did by cropping and enlarging the image on a PC. The zoomed image has less resolution and can appear grainy as compared to the unzoomed image. If you only have Digital Zoom, don t overuse it. You usually have better results cropping and enlarging the image on a PC. 30
On the previous slide, I stood in one location and used the zoom. On this slice, I moved forward and backward while I zoomed to keep the subject the same size. For the normal view in the left center, I chose a comfortable distance and set the lens to the normal setting. I noted how much of the field of view was taken up by the subject flowers. For the top photos, I moved closer to the subject and zoomed out to wide angle to fill the same amount of the field of view as the normal. Notice how the background has wider angle view. For the bottom view, I moved further back from the subject and zoomed in to telephoto to fill the same amount of the field of view as the normal. Notice in this case how the background has a narrower angle view. If the background is distracting, I might back up and use a telephoto setting to minimize how much of the background visible. If the background is pleasing, I might move in and use a wide angle setting to somewhat enhance the background. The photos on the right (and the bottom photo is covered by another photo in the above slide) show the same effect (moving and zooming) on a foreground object. 31
32
<C> An automatic camera can adjust the shutter speed, f-stop, and ISO setting to get the exposure that it determines to be correct. <C> The range of brightness from very dark to very bright situations is a huge range. No single control has that much range, so the camera uses a predetermined algorithm to decide what value to use. <C> If you go off fully automatic and set one of those settings to a particular value, the camera will (try to) adjust the other two controls to reach the exposure that it determines to be correct. <C> This table shows combinations of settings that result in the same exposure and notes the effect of each. <C> The bottom three photos were taken in rapid succession. The left photo used spot metering, using the side of the hill. Grass and leaves are middle gray green in that the brightness is the same as the camera wants to use. The center photo used center-weighted metering and the inclusion of some sky made the camera darken the image to reach it s preferred value. The right photo uses Matrix metering, checking the brightness in several zones around the frame, looking at bright spots and dark spots to determine exposure. (Don t assume that matrix metering will always work well.) <C> The metering method in a camera looks at whatever area selected (spot, center-weighted, matrix, etc.) and sets the controls to get Zone 5. 33
As we just noted, the camera will try to make the scene to be Zone 5 (middle gray). The upper-right rose, in front of a neutral background results in a good exposure on automatic. <C> The bottom-right pair of photos shows the result of a dark background. In order to make the overall scene Zone 5, the scene was brightened resulting in a dark gray background and overexposed rose. <C> The bottom-left pair of photos shows the results of a light background. In order to make the overall scene Zone 5, the scene was darkened resulting in a light gray background and underexposed the rose. Both can be fixed with a Photo Editor, but using the Exposure Compensation control can allow you to correct the exposure in the camera if you can estimate the needed correction. 34
In the example photos at the top, the area marked by the green rectangle is in good focus and the area marked by the red rectangles are in near focus. The larger aperture (smallest f-stop number) has the least area in focus (Depth of Field). Note that cameras preview with the aperture fully open, giving the brightest image for us to see, with the least Depth of Field to facilitate focusing. <C> The aperture or f-stop determines the range of area in front of and behind the focus point will be in focus. As seen, everything in that range is in focus, allowing us to preset the focus. The chart shows the near and far limits of good focus for two apertures focused a varying distances. Notice that more area behind the focus point is in good focus than in front. And note that at the narrow aperture (large f-stop number) has a point (marked by the green line) where everything behind the focus point and half the distance in front of the focus point are in good focus. There is no real need to focus beyond this Hyperfocal distance. <C> If you choose a f-stop that results in a slow shutter speed, you may need to adjust the ISO setting for a fast enough shutter speed to reduce blur from your shaking. <C> Generally a shutter speed of 1/125 second or faster will minimize blur fro m shaking. If your camera has a Vibration Resistant (or Vibration Compensating) lens, the shutter speed can be half that value or less. 35
The top pair of images show the effect of f-stop on a scene. The bright sunlight resulted in a small aperture (large f-stop number) with a large Depth of Field, and the background becomes distracting. Forcing a large aperture (low f-stop number) reduces the Depth of Field, forcing the background out of focus. <C> The middle pair of images show the effect of low light on shutter speed. The dark forest resulted in a slow shutter speed, even at the largest aperture. Setting the ISO to the fastest value resulted in a much faster shutter speed. Almost fast enough to freeze the wings. I must add that the fast ISO setting can result in a slightly grainy image. <C> The bottom pair of images show the result of intentionally forcing a slow shutter speed on moving water. Even on automatic, holding dark filters in front of the lens will slow the shutter speed. 36
The top-left photo was taken with a point and shoot digital camera from about four feet away. <C> The bottom-left photo is an enlargement. Stepping back and zooming in resulted in a narrower angle of view, with just enough background to give a good sense of presence in the tree. <C> The right pair of images are the result of moving in, using a wider angle lens, giving less Depth of Field, forcing the background well out of focus. <C> In those right images, the caterpillar is parallel to the lens, so it is easy to get the entire caterpillar in focus. The bottom-center photo head on (I hope do you know which end is the front?) shows how small the Depth of Field really is. 37
The small Depth of Field in close ups makes focusing difficult. A tripod can help those of us who can t help rocking back and forth. And often in auto focus mode, the camera can just see saw in an d out trying to focus. <C> Find an angle where the subject is parallel to the face of the lens. <C> The top-right image was taken from about three feet away, zoomed in, and has significantly more Depth of Field than the center-right image taken from maybe a foot away. <C> The bottom-right pair of images also show the shallow Depth of Field in close ups. I was on fully automatic and could not get the near and far flowers in focus at the same time. I should have forced a small aperture (large f-stop number). <C> The bottom-left pair of images show how I use the shallow Depth of Field in close ups to keep the viewer in the frame. The out of focus top edge makes the eye move back down. 38
39
40
41
We started with the question as to whether we could trust what we (think we) see. In order to speed things up as much as possible, we really only see the what our brain perceives as significant and fills in the rest of the details itself. This can lead to many of the Optical Illusions. Birds do not represent a threat (except to Alfred Hitchcock), so we typically glance over them. It takes a lot of study to see all of the birds. 42