Abstract

Hue and saturation scaling were used to measure the appearance of spectral lights as a function of stimulus size at loci spaced across the horizontal meridian. At a given locus, each hue (red, yellow, green, and blue) grew as a function of stimulus size up to some asymptotic value. Growth functions fitted to the hue data were used to derive the sizes of the "perceptive fields" of the hue mechanisms. We had previously investigated the size-scales of these fields by using stimuli presented on a dark background: Field sizes for all mechanisms increased with eccentricity, this increase was greater on the temporal than on the nasal retina, and the retinal size-scales of the different hue mechanisms were not the same. We now report the results obtained from repeating the study with stimuli embedded in a white surround. The main effects of the white surround were as follows: Sizes of perceptive fields of all mechanisms decreased at all peripheral loci, apparent saturation decreased for foveal stimuli but increased for peripheral stimuli, and short-wavelength redness increased everywhere.

© 1990 Optical Society of America