The pixels that make up a digital image each have an "address",
a code that defines color, brightness and shades. When we make images with a
digital camera or from film with a scanner we are creating a matrix of pixels
that altogether create the illusion of a continuous tone image. These codes
are not dyes or even densities, but specific information as to how the computer
will interpret the colors and tonal values on the screen. It is only when we
make a print that we leave the "digital" world and enter the world
of dyes and pigments. Because each pixel has a code, basically a bunch of information
that is composed of bits and bytes, we can alter that code to change the "address",
or color and tonal look of every pixel. In this lesson we'll use the Replace
Color dialog box, found in most versions of Photoshop, or under other names
in other programs, to illustrate the point and give you an easy, fun way to
play with your pictures.
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