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A-3 Desktop Color Primer
Many computer applications include dialog boxes in which you choose colors
by manipulating hue, saturation, and brightness. For example, Photoshop
uses a square Color Picker (plate 4) which can be reconfigured according to
your preference.
Additive and subtractive color systems
Color devices used in desktop publishing and printing simulate the range of
visible colors using a set of primary colors that are combined to create other
colors. There are two methods for creating a range of colors from a set of
primary colors. Computer monitors and scanners are based on the additive
color model. Printing technologies, including iR C2100/2100Ss and offset
presses, are based on the subtractive color model.
Additive (RGB) color
Color devices that use the additive color model make a range of colors by
combining varying amounts of red, green, and blue light. These colors are
called the additive primaries (plate 5). White is created by adding the
maximum amount of red, green, and blue light available. Black occurs
wherever all three colors are absent. Grays are created by adding equal
amounts of all three color together. Combining varying amounts of any two
of the additive primaries creates a third, saturated hue.
A familiar device that is based on this color model is the computer monitor
(plate 6). Monitors have red, green, and blue phosphors that emit varying
amounts of light to display a given color. Scanners create digital
representations of colors by measuring their red, green, and blue components
through colored filters.
Subtractive (CMY and CMYK) color
The subtractive color model is the basis for color printing and for color
photographic prints and transparencies. While the additive color model
simulates the visible spectrum of color by adding light of three primary hues,
the subtractive color model starts with a “white” or neutral light source
containing light of many wavelengths. Inks, toners, or other colorants are
used to selectively absorb (subtract) certain wavelengths of light that
otherwise would be reflected or transmitted by the media in use.