Nonlinear nature of the opponent‐color channels

Abstract

Abstract Heterochromatic brightness matches were made between bichromatic mixtures of Λ 1 and Λ 2 , and a 100‐trolands white reference light of 2° visual angle. A remarkable brightness reduction was found in the bichromatic mixtures, showing brightness additivity failure. The failure was especially large at the luminance ratio where hue cancellation occurred. The results were explained by assuming the brightness sensation to be mediated not only by the luminance channel but also by the red‐green and yellow‐blue opponent‐color channels, and by assuming further nonlinear transformation of responses in the opponent‐color channels.