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James A. Schirillo, Alexander D. Logvinenko; Lightness judgments made in shadow and highlight. Journal of Vision 2006;6(6):710. doi: 10.1167/6.6.710.
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An object's lightness is known to be relatively constant when its illumination varies. Lightness constancy is usually measured when the target is in highlight (and matching chips are in shadow), and for an illumination range of not more than 10:1. We have measured lightness constancy for 16 naïve subjects using a symmetrical display, where on different trials the target was placed in both highlight and shadow. The ratio of illuminations was ∼100:1. We found, first, a considerable difference between the results depending on the placement of the target (i.e., highlight vs. shadow). The Brunswick ratio when the target was in shadow (and matching chips were in highlight) was ∼41% (Thouless ratio = ∼80%). The Brunswick ratio when the target was in highlight (and matching chips were in shadow) was ∼99.8% (Thouless ratio = ∼97.8%). Second, when the target was in highlight near perfect lightness constancy was found, dramatically higher than ever reported.
Hsia (1943), in the only other symmetrical display we know of, also has data suggesting this trend. However, his illumination ratio only gets as large as 4.3:1. Also, the maximum Brunswick ratio obtained in his study was ∼53%. Thus, the dramatic effect we get using real papers and lights may be due to using such a large luminance ratio (∼100:1).
Y. Hsia. (1943). Whiteness constancy as a function of difference in illumination, Archives of Psychology. 284, 5-63.
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