Outlines of a Theory of Photopic Colorimetry (Part III): Advanced Colorimetry, or Full-Blooded Colorimetry (Second Article)

Abstract

There are familiar relations among colors which remain unrepresented in the affine geometry of basic colorimetry. An advanced colorimetry will incorporate maximum color similarity. Advanced colorimetry applies Riemannian geometry, not Euclidean geometry. A line element is proposed for color space; it preserves additivity of brightness. The line element bridges heterochromatic differences and just-noticeable differences in color. One problem is that the Bezold-Brucke phenomenon pervades this range of conditions; a correction factor must then be applied to the line element. Then two constraints conflict: the constraint that both large and small differences are accounted for, and the constraint that Fechner’s law holds uniformly across color space. This tension changes the theory of advanced colorimetry to a transitional theory or heuristic account.