Chromatic valence and hue sensation.

Red-green and yellow-blue chromaticnesses were scaled for various monochromatic lights by a just-noticeable-difference method. The just-noticeable difference of each chromaticness, i.e., redness, greenness, yellowness, or blueness, was defined by the change of the canceling light intensity that was required to produce a just-noticeable difference in the amount of the opponent-hue attribute of each monochromatic light. The results showed that an approximately logarithmic transformation took place at the two opponent-color coding systems and that there existed an interaction between red-green and yellow-blue opponent-color coding systems in such a manner that the effective contribution of one opponent-color response to the perceived opponent-hue attribute was reduced by increasing the magnitude of the other opponent-color response. This interaction is considered to be responsible for the well-known veiling effect.