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• a* - the red - green component, where +a* indicates red, and -a* indicates green, ranges
from -128 to +127.
• b* - the yellow - blue component, where +b* indicates yellow, and -b* indicates blue, ranges
from -128 to +127.
• The CIE L*C*h* uses L*, C*, and h* components where the C* and h* components are
calculated from the a* and b* coordinates of the CIE L*a*b* model.
A color has the same location in CIE L*C*h* and CIE L*a*b*, but uses different notations.
[313] CIE L*C*h*
The L*C*h* color space uses the following components:
• L* - the lightness component ranges from 0 to 100. The L* component is the same as in
L*a*b*.
• C* - the chroma component, the distance from the lightness axis, ranges from 0 at the axes
to more than 100 at the edge.
• h* - the hue angle, expressed in degrees, where 0° means the location on the +a* axis and
180° means the location on the +a* axis.
△E (Delta E)
The most general metric to express the difference between two colors in CIELAB is Delta E. The
Delta E value predicts how the human eye perceives the color difference.
Delta E does not always give enough information about differences between colors. Therefore,
most color evaluations also use other metrics. The interpretation of a Delta E value remains
subjective. The impact of a certain Delta E value depends on the application and even on the
color. For example, the human eye can better distinguish a difference between grayish colors
than between highly saturated colors.
h
L
C
Learn about color differences
Chapter 9 - Print what you expect
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