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The illustration
above is a representation of what the ranges of the Visible, RGB,
Pantone, and CMYK color gamuts look like relative to each other. Gamut
is defined as the range of all colors that can be expressed in a given
color system.
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The visible
color gamut, which is the range of colors the eye can see, includes
many more colors than the RGB (red, green and blue) gamut used to
show color on monitors. The gamuts that can be printed with premixed
inks (of the Pantone Matching System, for example) or with process
inks (CMYK) are even more limited.
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Artists
and graphics professionals who design for print have to consider the
differences between visible, display, and printing gamuts so that
they design with colors that can be reproduced with ink and paper.
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Red,
green, and blue are called additive colors because if light from each
of these colors is projected on each other, the result is all wavelengths
of visible light, or white light. A disadvantage of RGB color is that
reproducing color requires some kind of special device or projection
to display the colors.
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Cyan,
magenta, and yellow are subtractive colors because removing each of
these colors will result in all wavelengths of visible light, or white
light. In theory, mixing cyan, magenta, and yellow should give you
black. The reality of the situation is that minor impurities in the
inks may absorb color when the color should be reflected to the viewer.
The result is that the color reflected by the combination of the three
colors is a muddy brown. The compensation for the deficiencies found
in inks is the creation of an artificial independent black to help
achieve a real black. Black ink provides depth to the shadow areas
and enhances detail in the image overall.
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When
colors are translated from the RGB gamut of the computer screen to
the CMYK gamut of process printing inks, the CMYK range does a better
job of reproducing some colors than it does with others. For example,
more RGB greens than oranges can be successfully reproduced with process
inks.
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