Effect of yellow-tinted lenses on brightness.

Magnitude estimates of brightness were obtained for small (5-deg diameter) and large (15 deg X 20 deg) targets viewed through yellow-tinted lenses (ytl's) and luminance-matched neutral lenses. The results indicate that brightness perception with ytl's is up to 40% greater than that with neutral lenses when the spatial extent of the stimulus exceeds the fovea. The onset of the enhancement effect is coincident with the chromatic threshold, and its end point is coincident with psychophysical estimates of rod saturation. In a second experiment, brightness estimates were obtained for the ytl's and neutral lenses during the cone plateau of the dark adaptation curve when rods, but not cones, were desensitized by bleach. The brightness-enhancement effect was negligible. These results confirm the subjective impression that brightness perception is enhanced by ytl's and indicate that this effect is mediated, in large part, by the contribution of rod signals to the chromatic pathway.