Abstract
Three experiments investigated the role of physical illumination on lightness perception in simultaneous lightness contrast (SLC). Four configurations were employed: the classic textbook version of the illusion and three configurations that produced either enhanced or reduced SLC. Experiment 1 tested the effect of ambient illumination on lightness perception. It simulated very dark environmental conditions that nevertheless still allowed perception of different shades of gray. Experiment 2 tested the effect of the intensity of Gelb lighting on lightness perception. Experiment 3 presented two conditions that integrated illumination conditions from Experiments 1 and 2. Our results demonstrated an illumination effect on both lightness matching and perceived SLC contrast: As the intensity of illumination increased, the target on the black background appeared lighter, while the target on the white background was little affected. We hypothesize the existence of two illumination ranges that affect lightness perception differently: low and normal. In the low range, the SLC contrast was reduced and targets appeared darker. In the normal range, the SLC contrast and lightness matchings for each background were little changed across illumination intensities.
Highlights
We studied the effect of illumination on lightness perception in simultaneous lightness contrast (SLC) displays
As our research focused on the influence of physical illumination on the perception of achromatic surface color, we employed experimental setups that envisage both types of failures by combining different types of SLC displays—capable of generating different perceptual effects on targets that are physically identical—with two types of illumination that can both be found in nature: ambient and direct
With the exception of the configuration reduced, the other two modified SLC configurations gave rise to lightness matches that were in line with the configuration classic
Summary
We studied the effect of illumination on lightness perception in simultaneous lightness contrast (SLC) displays. It is well established that lightness perception is greatly influenced by field factors—including local and global luminance ratios, and perceptual grouping—rather than by the luminance of an achromatic surface itself (Gilchrist, 1994, 2006) This is desirable because luminance (i.e., the amount of light reflected away from a surface) is a variable source of visual information, whereas it is reasonable to assume that the goal of the visual system is to generate a model of the world in which an object’s structural features stay more or less constant despite changes over time in the retinal image (Zavagno, Daneyko, & Actis-Grosso, 2015). This is the phenomenon that goes by the name perceptual constancy
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