Bezold-Brücke hue shift and nonlinearity in opponent-color process

Dependence of the red-green and yellow-blue opponent-color responses on stimulus intensity was examined. First, each of four chromatic responses was measured as a function of illuminance by using a hue cancellation procedure. The cancellation redness and greenness increased proportionally with illuminance, but the cancellation yellowness and blueness did not. Second, the relative growth rate with illuminance between the two opponent-color systems was determined by using a technique of the estimation of hue ratio. The result gave a support to the view that the Bezold-Brücke hue shift is contributed mainly by the opponent-colors neural interactive process. It was suggested that the nonlinear transduction of the yellow-blue system, producing the hue shift, might have a close relation to the change with stimulus intensity in the relative sensitivity of the short-wavelength cone mechanism to the long- and middle-wavelength cone mechanisms.