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Chapter 8: Color
About color
About colors in digital graphics
We use color models to describe the colors we see and work with in digital graphics. Each color model, such as RGB,
CMYK, or HSB, represents a different method for describing and classifying color. Color models use numeric values
to representthe visiblespectrumofcolor.A color space is avariant of acolor modeland hasaspecific gamut (range)
of colors. For example, within the RGB color model are a number of color spaces: Adobe RGB, sRGB, and Apple
RGB. While each of these color spaces defines color using the same three axes (R, G, and B), their gamuts are
different.
When youworkwiththe colors in agraphic,you areactuallyadjusting numericalvaluesinthe file.It’seasytothink
of a number as a color, but these numerical values are not absolute colors in themselves—they only have a color
meaning within the color space of the device that is producing the color.
Becauseeachdevicehas itsown colorspace,itcan reproducecolorsonlyinits gamut. When an imagemoves from
one device to another, image colors may change because each device interprets the RGB or CMYK values according
to itsown colorspace.For example, it is impossible forall thecolorsviewedonamonitortobeidentically matched
in a print from a desktop printer. A printer operates in a CMYK color space, and a monitor operates in an RGB color
space. Their gamuts are different. Some colors produced by inks cannot be displayed on a monitor, and some colors
that can be displayed on a monitor cannot be reproduced using inks on paper.
Even though it is impossible to perfectly match all colors on different devices, you can use color management to
ensure that most colors are the same or similar enough so they appear consistent.
See also
“About color management in Adobe applications” on page 200
“To synchronize color settings across Adobe applications” on page 202
About RGB
A large percentage of the visible spectrum can be represented by mixing red, green, and blue (RGB) colored light in
various proportions and intensities. Where the colors overlap, they create cyan, magenta, and yellow.
RGB colors are called additive colors because you create white by adding R, G, and B together—that is, all light is
reflected back to the eye. Additive colors are used for lighting, television, and computer monitors. Your monitor, for
example, creates color by emitting light through red, green, and blue phosphors.
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