Bezold–Brücke effect and visual nonlinearity*

Abstract

This paper reports an investigation of the Bezold–Brücke effect as a means of studying nonlinearity in vision. Two subjects performed hue-matching experiments using simultaneously presented monochromatic stimuli of unequal corneal irradiances. For seven wavelengths between 560 and 620 nm, the shift of hue was measured over a 1000:1 range of irradiances, in steps of about 3:1. Contrary to previous reports of the Bezold–Brücke hue shift, the hue of a given wavelength is not a monotonic function of irradiance, nor is there an invariant wavelength in this spectral region. Some previous models of the Bezold–Brücke effect in the literature are incompatible with the present data. We propose a physiologically plausible, analytic form for nonlinearities of the red and green color systems, and a simple model for the physiological correlate of hue, which together are capable of predicting some major characteristics of the present data and of previously reported data.