Perceived lightness of chromatic object colors including highly saturated colors

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Abstract
A model was formulated for predicting the Helmholtz‐Kohlrausch effect or the Y tristimulus values for chromatic object colors with the same perceived lightness (L/Y ratios). the model was extended from the previous one in Color Res. Appl. 16, 16‐25 (1991), making it possible to estimate the Helmholtz‐Kohlrausch effect on chromatic object colors with any Munsell Value. By analyzing the two experiments by Wyszecki and by Sanders and Wyszecki using the extended model, the model parameters were estimated for each experiment. By using each of the two estimated equations, L/Y ratios for Y = 20.0 were predicted in the whole chromaticity gamut corresponding to the two kinds of experimental results. the derived contour lines for equal L/Y ratios correlated well with those estimated directly from each experimental data. In addition, extrapolated L/Y ratios for spectral colors with Y = 20.0 showed very good agreement with the luminance ratios for equally bright spectral stimuli, so‐called brightness/luminance (B/L) ratios, derived from the luminous efficiency functions Vb,2(Λ) by CIE TC 1‐02 and Vjudd(Λ) proposed by D. B. Judd.