Color and Brightness Constancies dependreciprocally on Saturation

Color and brightness constancies may not be independent, since increasing a sample saturation should decrease the demand on the color constancy and increase that on the brightness constancy [Color Res. Appl.43, 630 (2018)CREADU0361-231710.1002/col.22227]. We tested this claim using color and brightness constancy data from Foster et al. [Vis. Res.41, 285 (2001)VISRAM0042-698910.1016/S0042-6989(00)00239-X], whose observers made side-by-side and successive comparisons of central patches (“asymmetric matches”) presented in pairs of identical Mondrian displays with simulated illuminants of 25000 K and 6700 K daylights. Saturations (CIE “chroma”) of the central patches varied from 0.007 to 0.092. For most observers (as in a toy Gaussian model of the surface reflectance spectra), increasing saturation reduced color constancy and increased brightness constancy.