pigmented colorants: dependence on media and time - Cornell ...

epresentation of converting a reflected light stimulus to XYZ primaries via color
matching functions is seen in Figure 3.19.
It is important to note that spectral reflectances contain more information than
do the tristimulus values. Then, it is possible for two materials with reflectances
R1(λ) = R2(λ) to have the same color (have identical XY Z values) under light
source H1(λ). However, these two materials will not match under a different light
source H2(λ). Two materials that look identical under one lighting condition,
but not another are known as metamers. An example of metameric stimuli are
illustrated in Figure 3.20.
Figure 3.20: An example pair of metameric stimuli. The two stimuli produce
equivalent stimulations of the eye’s photoreceptors when viewed
under identical lighting conditions, but they have different spectral distributions.
Adapted from [GM97].
Another important tool for color analysis is the Chromaticity Diagram. Chro-
maticity coordinates provide hue and saturation information independent of lumi-
nance. The XY Z chromaticities are given by:
71