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Updated: Aug 9, 2026

Measuring Spatially- and Directionally-varying Light Scattering from Biological Material
Published on: May 20, 2013
Photometric, geometric, and perceptual factors in illumination-independent lightness constancy
Alessandro Soranzo1, Tiziano Agostini
1School of Social Sciences and Law, University of Teesside, Middlesbrough TS1 3BA, England. a.soranzo@tees.ac.uk
Abstract:
It has been shown that lightness constancy depends on the articulation of the visual field (Agostini & Galmonte, 1999). However, among researchers there is little agreement about the meaning of "articulation." Beyond the terminological heterogeneity, an important issue remains: What factors are relevant for the stability of surface color perception? Using stimuli with two fields of illumination, we explore this issue in three experiments. In Experiment 1, we manipulated the number of luminances, the number of reflectances, and the number of surfaces and their spatial relationships; in Experiment 2, we manipulated the luminance range; finally, in Experiment 3 we varied the number of surfaces crossed by the illumination edge. We found that there are two relevant factors in optimizing lightness constancy: (1) the lowest luminance in shadow and (2) the co-presence of patches of equal reflectance in both fields of illumination. The latter effect is larger if these patches strongly belong to each other. We interpret these findings within the albedo hypothesis.
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