Datacolor 45IR User Guide, 5.2014, Version 1.0 (4230-0402M)
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Description of the Colorimetric functions
The Datacolor 45IR calculates and displays colorimetric values as well. Measurements in
colorimetry
modes
have the advantage of an absolute description of color based on characteristic values.
CIELAB
The most popular color system in the printing industry is the CIE L*a*b* color
space. Every color is precisely described by three values: The L* value stands
for the luminance and can have values between 0 (a theoretical, absolute
Black) and 100 (a theoretical, ideal White). The a* value describes the color
value on the Green/Red-axis (- a*: Green, + a*: Red) and the b* value the
color value on the Blue/Yellow axis ( - b*: Blue, + b*: Yellow).
CIELAB, colorimetric measurement on a blue sample. The blue color has a
low luminance of L = 28.71 and a low portion of Red (a < 15).
In colorimetry the white reference is absolute, contrary to densitometry where the white is usually referenced
to paper white. Before making colorimetric measurements, an absolute white calibration has to be performed
by placing Datacolor 45IR on the charging console and calibrating on the round, white ceramic standard.
Colorimetric measurements can only be compared when the measurement conditions are the same:
o
White reference: Absolute
o
Illuminant: D50
o
Observer: 2°
