Adams Chromatic Valence Color Space

Adams chromatic valence color spaces are a class of color spaces suggested by Elliot Quincy Adams. 

Two important Adams chromatic valence spaces are CIELUV and Hunter Lab.

Chromatic value/valence spaces are notable for incorporating the opponent process model, and the empirically-determined 2½ factor in the red/green vs. blue/yellow chromaticity components (such as in CIELAB).

In 1942, Adams suggested chromatic value color spaces. Chromatic value, or chromance, refers to the intensity of the opponent process responses, and is derived from Adams' theory of color vision.

A chromatic value space consists of three components:

·         {\displaystyle V_{Y},}V_Y the Munsell-Sloan-Godlove value function: {\displaystyle V_{Y}^{2}=1.4742Y-0.004743Y^{2}}(V_Y)² = 1.4742Y – 0.004743Y²

·         {\displaystyle V_{X}-V_{Y}}V_x – V_y,  the red-green chromaticity dimension, where {\displaystyle V_{X}}V_x is the value function applied to {\displaystyle (y_{n}/x_{n})X}(y_n/x_n)X  instead of Y

·         {\displaystyle V_{Z}-V_{Y}}V_Z - V_Y, the blue-yellow chromaticity dimension, where {\displaystyle V_{Z}}V_Z is the value function applied to {\displaystyle (y_{n}/z_{n})Z}(y_n/z_n)Z  instead of Y

A chromatic value diagram is a plot of {\displaystyle V_{X}-V_{Y}}V_X - V_Y (horizontal axis) against {\displaystyle 0.4(V_{Z}-V_{Y})}0.4(V_Z – V_Y) (vertical axis). The 2½ scale factor is intended to make radial distance from the white point correlate with the Munsell chroma along any one hue radius (i.e., to make the diagram perceptually uniform). For achromatic surfaces, {\displaystyle (y_{n}/x_{n})X=Y=(y_{n}/z_{n})Z}(y_n/x_n)X = Y = (y_n/z_n)Z  and hence {\displaystyle V_{X}-V_{Y}=0}, {\displaystyle V_{Z}-V_{Y}=0}V_X – V_Y = 0, V_Z – V_Y = 0. In other words, the white point is at the origin.

Constant differences along the chroma dimension did not appear different by a corresponding amount, so Adams proposed a new class of spaces, which he termed chromaticvalence. These spaces have "nearly equal radial distances for equal changes in Munsell chroma".