Graphics Programs Reference
In-Depth Information
Characterization: The process of measuring the way in which a device
behaves. When a user profiles a device, he or she is producing a charac-
terization or fingerprint of how that device produces tone and color.
Chroma: The C component of the LCH (luminance/chroma/hue) color
model. Chroma is similar to saturation, and sometimes is referred to as
colorfulness. It describes the purity of a specific hue at a specific light-
ness. No chroma would be a gray, low-chroma pastel; high chroma, a
vivid pure hue.
Chromaticity: Collectively, the x and y components of the CIE 1931 x,y,Y
color space (or Chromaticity values). It can also refer to the u - ,v - com-
ponents of the CIE 1976 L* u - ,v - color space. These color spaces are
directly related to the CIE XYZ color-matching functions. As such, a chro-
maticity describes the ratio of intensities on the cone receptors of the
standard human observer. The intensity or total luminance of this ratio
is not a part of chromaticity; the Y or L* component must be added to
define the exact sensation at the retina. Also known as Chromaticity
coordinates. See also Chromaticity diagram .
Chromaticity diagram: A diagram of the x,y components of CIE 1931 XYZ
colorspace or the u - ,v - components of the CIE 1976 L* u - ,v - color space.
Device gamuts often are plotted on a Chromaticity diagram.
CIE (Commission Internationale de L'Éclairage): Also known as Interna-
tional Commission on Illumination. An international standards body
accepted by the ISO that defines the international standards for illumi-
nation and color science. The methods for measuring color fall under the
scope of their work; the CIE also is involved with tasks such as stan-
dardizing the color and intensity of traffic signals, streetlights, and light
bulbs. The tests done by this group formed the basis for much of the color
science used today in color management systems including the work of
producing a number of synthetic color spaces. See also CIELAB and
Illuminant .
CIELAB: A synthetic color space defined by the CIE in 1976. CIELAB was
an attempt to create a spatially uniform color space to be used for math-
ematical conversion of color between dissimilar mediums. Based on work
done by the CIE, a number of mathematical models of color were pro-
duced over the years including CIELAB, CIE XYZ (1931), and so forth.
CIELAB is an update to the original model created in 1931 and uses three
synthetic primaries represented as L* (luminance), a* (red through green
colors), and b* (yellow though blue colors). This space is a uniformly dis-
tributed device-independent color space, meaning an equal distance in
the space produces an equal visual color difference. Also referenced as
CIE Lab. See also LAB .
CIE Standard Illuminants: See Illuminant .
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