Digital Cameras Overview While silver-halide film has been the dominant photographic process for the past 150 years, the use and role of technology is fast-becoming a standard for the making of photographs. Digital capture technology, including film scanners and digital cameras, is continuing to improve to a point where in a variety of applications, including commercial, photojournalism and consumer, digital cameras are superseding the use of film. Digital camera capture provides immediacy and cost-efficiency. However, there are a number of factors to consider in determining which digital camera to utilize, including its use and role in the picture-making process, the level of desired image quality and cost. Types of Digital Camera Capture Determining which digital camera to purchase and use can be a daunting task in consideration of the constant flux of improving technologies. There are basically four categories of digital camera capture, including disposable point and shoot, point and shoot (consumer and prosumer), digital singlelens reflex, digital backs for analog devices such as medium format and large format. Disposable digital Consumer point and shoot Prosumer point and shoot Disposable Digital Consumer and Prosumer Point and Shoot The disposable digital camera is the least expensive camera available and as such offers minimal features and the lowest image quality available. The camera allows for the image to be deleted just after exposure. A variation of the camera allows for the image to be reviewed on an LCD display after exposure. Upon completion of the filling the memory card, usually 23 images, the camera is dropped off and the resulting JPEG images can be burned onto a CD-R as well as printed to 4 x 6. The memory card is then erased and the camera is repackaged for future use. The consumer and prosumer point and shoot digital cameras are primarily targeted to the consumer market. The cameras, generally 3 to 7 megapixels, operate with largely automated functions, have non-interchangeable lenses and capture JPEG files of various levels of quality. The more sophisticated, prosumer digital cameras offer manual overrides for exposure and lens focus, and some are even capable of utilizing the RAW file format.
Digital Single-lens Reflex (SLR) Digital single-lens reflex cameras are based on conventional 35mm analog camera design, and are rather sophisticated in incorporating both automated and manual functions. All accept interchangeable 35mm lenses. The cameras range from typically 6 megapixels up to 12 megapixels and utilize both RAW and JPEG (JPG) file formats. Digital Backs Digital backs can be utilized on many medium-format cameras, including Hasselblad and Mamiya, and typically range from 6 megapixels up to 22 megapixels. The backs have the latest state-of-the-art technology, including the use of multiple captures and as a result are found in commercial environments due to their high cost. Digital Image Structure Sensors The digital image is typically made on a CCD (charged coupler device) sensor or a CMOS (complementary metal oxide semiconductor found in Canon and Kodak digital slr s) sensor in a single shot. The sensors generate pixel color values by averaging one red, one blue, and two green pixel sensors in a 2 x 2 mosaic structure. Because of this structure, the capture data must be interpretated in order to produce a smooth result. With the red and blue sensor values, 75% of the color values for each of these sensors is guessed, while with the green sensor values, only 50% of the color value is guessed because there are two green pixel sensors. Once the raw image is processed, the underlying pattern is not seen. However, with subjects containing fine edge detail, moiré patterns or color fringing is possible.
Multiple capture cameras are capable of recording sequential exposures of red, blue and green. As a result, each pixel is based on 100% color information and there is no pixel guesswork. In addition to the number of pixels the sensors are capable of capturing, the physical size, ranging from 14 x 21 mm to 24 x 36 mm will determine the magnification of the lens. If the sensor is smaller than 24 x 36 mm, the magnification factor will increase approximately x1.5. Therefore, a 28 mm wide-angle lens that is used on an analog 35 mm camera will behave more like a 35 mm semi-wide angle lens. Megapixels One of the most important components of a digital camera system is the number of megapixels or the number of pixels the sensor can capture. For example, a 3028 x 2000 pixel camera, such as the Nikon D70, can capture approximately 6 million pixels and is commonly referred to as 6 megapixels. However, these numbers can be deceiving as not all of the pixels are used to capture the image, and the effective number of pixels that a camera uses is more accurate in determining pixel dimensions. While the number of megapixels a camera can capture is increasing to upwards of 16 megapixels, it will be necessary to account for the smaller sensor size to fit more pixel sensors into a 35 mm frame area. Such cameras will run the risk of being less efficient at collecting light due to the smaller pixel sensors, resulting in increased noise (artifacts found in digital images, particularly in low light-level images). Memory Cards Memory cards is another important component of a digital camera system, and specifically, their read/write speed specifications and the speed in which digital images can be transferred from the camera to the computer. Memory cards typically come as 32 MB, 64 MB, 128 MB, 256 MB, 512 MB and 1 GB and will determine the number of images that can be made/stored while shooting. In utilizing RAW format or high-quality JPEG (JPG) format, it is recommended to utilize memory cards of at least 512 MB capacity. So as to limit the possibilities of memory card failure, it is recommended to utilize no more than 90% of the capacity and always reformat the card in the camera before shooting a new batch of images. With most digital cameras, the digital images can be transferred directly from the camera to the computer with either USB or Firewire connectivity or with a memory card reader. Resources Additional information and resources on digital camera capture can be found at the following websites: www.dcsource.com www.dpreview.com www.adobe.com/products/photoshop/main.html
Digital Workflow In considering the digital workflow, it is important to give specific attention to an image archive and management as well as the color management. In an analog environment, typically, the workflow went from film to contact sheet to print. Within the digital workflow, the image archive and overall management of the image files can become overwhelming in an instant. Adobe Bridge Within Adobe Creative Suite CS2, the Bridge application is designed to provide a navigational link between CS2 applications as well as function as a useful image management tool. Other applications useful for image management include Apple s iphoto for Mac OS X and Adobe s Photoshop Album for PC users. Apple iphoto
RAW and JPG mode Nearly all digital single-lens reflex cameras and some prosumer digital cameras are capable of shooting in both RAW and JPG (with varying levels of image compression) mode. In shooting in the RAW mode, the digital image file is essentially the data that the camera s chip has recorded. It is comparable to the latent image contained in an exposed, but undeveloped, piece of film. The RAW file is considered the equivalent of a digital negative (DNG format). Since the white balance has not been set with a RAW file, the photographer can adjust the color temperature balance without any image degradation. Possibly the biggest advantage of shooting RAW is that photographers have 16-bit images (post raw processing to work with. A 16-bit file has 65,536 levels of brightness to work with compared to a JPG file s 8-bit space with just 256 brightness levels. Some of the drawbacks in shooting in RAW mode are longer in-camera write times to the memory card and larger files resulting in lower memory card capacity. In shooting in the JPEG (JPG) mode, the files are smaller and as a result more can fit on a memory card. For many circumstances, such as family images or news photos, the image quality is sufficient and in many cases can produce very high quality prints. Due to their small size, the JPG files are easily transmittable on the web. Adobe Photoshop CS2 Camera Raw The Camera Raw plug-in is an important tool in adjusting the white balance, exposure, shadows, brightness, contrast, saturation, detail characteristics including luminance smoothing and noise reduction, chromatic aberration, characteristic curves and color calibration with both single files and multiple RAW mode files. With CS2 Camera Raw 3.0, photographers are able to create basically the equivalent of digital negatives, DNG format files, for future use in various image optimization applications as the technology continues to evolve. Files can be scaled up without any file deterioration. Resource In addition to the recommended supplementary text, Adobe Photoshop CS2 for Photographers, the following book may be helpful in providing additional information on the use of the Camera Raw 3.0 plug-in: Real World Camera Raw, Bruce Fraser (Peachpit Press 2004)