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

andwidth as converted signals are sent to the lateral geniculate nucleus and visual
cortex for further processing.
Figure 3.27 shows a plot of both the L ∗ u ∗ v ∗ and L ∗ a ∗ b ∗ color spaces. The solid
in the center is the region occupied by the colors reflected by the CIE Illuminant
D65.
Figure 3.27: Nonlinear color spaces; left: L ∗ u ∗ v ∗ and right: L ∗ a ∗ b ∗ .
Adapted from [G95a].
By design, the Euclidean distance between any two colors, A and B, in either
perceptual color space may be computed from the magnitude of the vector between
the colors:
E ∗ uv =
E ∗ ab =
84
(L∗ A − L∗ B )2 +(u∗ A − u∗ B )2 +(v∗ A − v∗ B )2
(L∗ A − L∗ B )2 +(a∗ A − a∗ B )2 +(b∗ A − b∗ B )2 (3.12)
The important feature of these spaces is that two pairs of colors with the
same distance metric between them are almost perceptually different by the same
amount. While neither of the two spaces is perceptually completely uniform, they
are close. Work continues on developing more uniform spaces.