Individual differences of the contribution of chromatic channels to brightness.

Perceived brightness is considered to be a combined consequence of outputs of the luminance channel and the chromatic channels in the visual system. The differences of logarithmic spectral luminous efficiencies between heterochromatic brightness matching and flicker photometry that were obtained from 16 subjects were examined by using principal component analysis. The luminous-efficiency difference between the two methods is described by only two principal components. Individual characteristics of the contribution of chromatic channels to brightness can be specified by measuring luminous efficiencies at 470 and 660 nm.