The consequences of opponent rectification: the effect of surround size and luminance on color appearance

Smith and Pokorny (Vision Res. 36 (1996) 3087.) described conditions under which chromatic contrast induction can reveal a hiatus, a region of chromat icity space which appears neither reddish nor greenish when presented in a chromatic equiluminant surround. The current study investigated the effect of varying the size and the luminance of the inducing surround. The color a ppearance of test stimuli in chromatic surrounds was assessed by asymmetric color matching to a comparison display. Equiluminant (12 cd/m(2)), 1 degre es square stimuli were generated on a CRT display and presented haploscopic ally. Ten test fields varied in their L-cone excitation along a constant S- cone line. The chromatic surrounds were of either high (red) or low (green) L-cone excitation on a constant S-cone line. In Experiment 1, surrounds we re 1.1 degrees, 1.5 degrees, 2.0 degrees. or 3.0 degrees square (surround w idths of 3 ', 15 ', 30 ', 1 degrees). In Experiment 2, the test and compari son surrounds were at higher (16.7 cd/m(2)) or lower (8.3 cd/m(2)) retinal illuminance than the test field. Contrast induction reached an asymptote fo r surround widths of 30 ' or larger. The amount of induction decreased for the surround widths of 15 ' and 3 '. The hiatus was present for the larger surrounds and decreased as surround size decreased. The use of a higher or lower surround luminance did not affect the magnitude of induction or the s ize of the hiatus. (C) 2001 Elsevier Science Ltd. All rights reserved.