Visual segmentation of a heterochromatic field into center/surround components.
The process of visual segmentation was studied by quantitatively estimating the apparent difference (i.e. the perceptual contrast) between two segments of a heterochromatic field. A chromatic test bar (Munsell 5R 6/6, 5BG 6/6, 5Y 6/6, or 5PB 6/6) was centered in an achromatic surround (Munsell N6) and the luminance contrast between the test bar and surround was varied between 0 and 39%. At equiluminance (0% luminance contrast) the chromatic border between center and surround was vague and perceptual contrast was minimal. When luminance contrast was increased slightly (5-15%) the border between center and surround was more distinct and perceptual contrast was almost two times greater than predicted by a model that combines spatial differences in chromaticity and luminance as orthogonal vectors. A luminance border may enhance perceptual contrast by increasing the salience of the center/surround hue difference. A vector model is consistent with perceptual contrast only at relatively high luminance contrasts, where hue differences play a relatively minor role in visual segmentation.
Sternheim
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Department of Psychology, University of Maryland, College Park 20742.
Penn
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RP
D003118:Color Perception / Q000502:physiology*; D006801:Humans; D008029:Lighting; D008297:Male; D008954:Models, Biological; D011601:Psychophysics