Size matters: Improved color‐difference estimation for small visual targets

Abstract— A long‐standing problem in color science is the accurate estimation of color differences for visual targets of small angular subtense. For instance, “What is the magnitude of a 0.5° color difference that will be as discriminable as a given 2° color difference?” Or, “What is the reduced angular subtense (or increased distance) at which two visual fields of given colors will become appreciably less discriminable than they were at larger subtense (or smaller distance)?” Past attempts at solving this problem have been specific to a particular color‐difference equation and, as such, the work lost relevance as improved color‐difference formulae were developed. This article proposes a structural model based upon the response of retinal cone cells to small‐subtense symbol images scattered by the ocular media. The method is demonstrated to be applicable without alteration to very different contemporary color‐difference equations, to be practical with a wide range of surround intensities, and to have high correlation with human search performance involving small color symbols on an electronic information display.