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Chapter 14: Color management
Understanding color management
Why colors sometimes don’t match
No device in a publishing system is capable of reproducing the full range of colors viewable to the human eye. Each
device operates within a specific color space that can produce a certain range, or
gamut
, of colors.
A color model determines the relationship between values, and the color space defines the absolute meaning of those
values as colors. Some color models (such as CIE L*a*b) have a fixed color space because they relate directly to the
way humans perceive color. These models are described as being
device-independent
. Other color models (RGB,
HSL, HSB, CMYK, and so forth) can have many different color spaces. Because these models vary with each
associated color space or device, they are described as being
device-dependent
.
Because of these varying color spaces, colors can shift in appearance as you transfer documents between different
devices. Color variations can result from differences in image sources; the way software applications define color;
print media (newsprint paper reproduces a smaller gamut than magazine-quality paper); and other natural varia
tions, such as manufacturing differences in monitors or monitor age.
CMYK
RGB
A
B
C
Color gamuts of various devices and documents
A.
Lab color space
B.
Documents (working space)
C.
Devices
What is a color management system?
Color-matching problems result from various devices and software using different color spaces. One solution is to
have a system that interprets and translates color accurately between devices. A color management system (CMS)
compares the color space in which a color was created to the color space in which the same color will be output, and
makes the necessary adjustments to represent the color as consistently as possible among different devices.
A color management system translates colors with the help of
color profiles
. A profile is a mathematical description
of a device’s color space. For example, a scanner profile tells a color management system how your scanner “sees”
colors. Adobe color management uses ICC profiles, a format defined by the
International Color Consortium
(ICC)
as a cross-platform standard.
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