Lightness decrease and increase in square-wave grating

Abstract

Lightness of low- and high-reflectance phases in square-wave gratings was measured and compared with that of uniform fields with the same reflectance. An enhancement of the lightness difference between the two phases of the grating was observed. The high-reflectance phase with 50% reflectance appeared to be darker than a uniform field of same reflectance, and even darker than a uniform field of 40% reflectance. As the difference in reflectance increased, however, the lightness at the high-reflectance phase changed from darker to lighter than that of the uniform field with the same reflectance. Thus, decrease and increase of lightness at the highreflectance phase of square-wave gratings depended upon the reflectance difference within the pattern. The enhancement of lightness difference and the lightness decrease of total area support the concept of a compound process of two types of inhibition: antagonistic excitation/ inhibition and nonantagonistic inhibition. © 1984 Psychonomic Society, Inc.