Abstract

Color vision in the periphery is improved by increasing stimulus size. However, can the sizes of peripheral stimuli be scaled to elicit equivalent sensory functions? Is it possible to equate peripheral functions to each other even though none of them is like the foveal function? Many of the size scales that have been developed simply specify the factors by which peripheral stimuli have to be increased. However, the specified peripheral sizes may not be necessary—smaller may be sufficient at any locus: these scales should be referred to the minimal size for a particular foveal function. We will reexamine existing discrimination and matching data, as well as our own estimates of color appearance from hue and saturation scaling. We will show that the size scales are not the same for all sensory qualities: different aspects of peripheral color vision may be determined at different levels of the visual system. We will describe the necessary constraints imposed by these findings on physiological models by using a very general opponent-process model, the spectral loci of the unique hues can be used to derive the ratios of the different cone types and test how their combinations are affected by size at each of the peripheral locations.

© 1992 Optical Society of America