ChApter 1. digitAl CAmerAs & imAges
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Each time you take a picture, millions of calculations are made in just a
few seconds. It’s these calculations that make it possible for the camera to
interpolate, preview, capture, compress, filter, store, transfer, and display
the image. All of these calculations are performed in the camera by an image
processor that’s similar to the one in your desktop computer, but dedicated
to this single task. How well your processor performs its functions is criti-
cal to the quality of your images but it’s hard to evaluate advertising claims
about these devices. To most of us these processors are mysterious black
boxes about which advertisers can say anything they want. The proof is in the
pictures.Cameras with the latest programmable image processors can be programmed
by camera companies to perform a variety of functions. Currently these
functions include in-camera photo editing and special effects such as red-eye
removal, image enhancement, picture borders, stitching together panoramas,
removing blur caused by camera shake, and much more.
When a camera company programs its processors its goal isn’t to exactly
reproduce a scene’s colors. Instead, using a process called color rendering,
its goal is to create what the programmers believe will be a pleasing repro-
duction. Frequently the contrast and color saturation are boosted, especially
in the midtones and specular highlights are compressed for printing and
viewing on typical displays. The processed images can be so distinctive that
it’s possible for some people to tell when an image was taken with a Canon or
Nikon camera.There are at least 256
tones captured for each
color—red, green, and
blue. Only one tone at
the shadow (black) end
of the range and one
at the highlight (white)
end are pure and have
no detail.