A Metric of Color

Abstract

Color space is a generalization of the color diagram; it embodies the laws of color mixture for human color vision. If it is based on color-matching judgments alone, the color metric is an affine geometry of a spatial pencil of vectors having a common origin. (Its projective representation is less clear and less useful as confined to a color plane or a color triangle.) A metric of color implies a line element for differences of color. The line element should reconcile the results of strongly heterochromatic photometry with those of photometry which proceeds by just-noticeable differences. There is an assumption implicit in the some versions of the line element: that the Weber–Fechner law holds precisely true over the entire color space. This summary article presages Schrodinger’s detailed development of colorimetry, published shortly afterward.