Simple estimation methods for the Helmholtz?Kohlrausch effect

Abstract

Four kinds of simple estimation equations are proposed for the Helmholtz—Kohlrausch effect. Two of them can be used for luminous colors, and the other two for object colors. In each of luminous and object colors, the two estimation equations are given to each of the Variable-Achromatic-Color (VAC) and the Variable-Chromatic-Color (VCC) methods. All the equations are similar in type to the Ware—Cowan equation. They give the ratio between luminance (or metric lightness) of test color stimulus and its equivalent luminance (or equivalent lightness) directly. Though their computations are simple, they can apply to various H—K effects including their adapting luminance dependency. The applicable fields of the proposed equations are wider than those of the Ware—Cowan equation. The proposed equations can be applied to predict the H—K effect within the whole chromaticity gamut including spectral colors, spectral luminosity functions based on direct color matching from 0.01 Td to 100 000 Td using the photopic and the scotopic spectral luminosity functions specified by CIE, equivalent lightness values of NCS colors, and others. © 1997 John Wiley & Sons, Inc. Col Res Appl. 22, 385–401, 1997