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Adobe Acrobat Help
Managing Color in Acrobat
Using Help
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232
CMYK model
Whereas the RGB model depends on a light source to create color, the CMYK model is
based on the light-absorbing quality of ink printed on paper. As white light strikes trans-
lucent inks, a portion of the spectrum is absorbed. Color that is not absorbed is reflected
back to your eye.
Combining pure cyan (C), magenta (M), and yellow (Y) pigments would result in black by
absorbing, or subtracting, all colors. For this reason they are called
subtractive
colors. Black
(K) ink is added for better shadow density. (The letter
K
came into use because black is the
key
color for registering other colors, and because the letter B also stands for blue.)
Combining these inks to reproduce color is called
four-color process printing
.
Subtractive color (CMYK)
Grayscale model
Grayscale uses tints of black to represent an object. Every grayscale object has a
brightness value ranging from 0% (white) to 100% (black). Images produced using black-
and-white or grayscale scanners are typically displayed in grayscale.
Grayscale also lets you convert color artwork to high-quality black-and-white artwork. All
color information in the original artwork is discarded; the gray levels (shades) of the
converted objects represent the luminosity of the original objects.
When you convert grayscale objects to RGB, the color values for each object are assigned
that object’s previous gray value.You can also convert a grayscale object to a CMYK object.
Color gamuts
The
gamut,
or color space, of a color system is the range of colors that can be displayed or
printed. The spectrum of colors that can be viewed by the human eye is wider than any
method of reproducing color.