Surround articulation II Lightness judgments

It has been hypothesized that to achieve color constancy, lightness judgments require an estimate of the illuminant. A companion paper [J. Opt. Soc. Am. A 16, 793 (1999)] suggests that surround articulation enhances the likelihood that a global luminance edge will be interpreted as being due to changes in illumination rather than in reflectance. Articulation is the process of adding equally spaced incremental and decremental patches within a surround while preserving the surround's space-average luminance. Such a process results in lightness judgments that correlate perfectly with equal local ratio matches. For decrements, lightness constancy does not require articulation. These findings help explain why Arend and Goldstein [J. Opt. Soc. Am. A 4, 2281 (1987)] obtained color constancy with complex Mondrian surrounds but not with simple center surrounds.