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| Volume 4, Number 9, Article 9, Pages 779-797 |
doi:10.1167/4.9.9 |
http://journalofvision.org/4/9/9/ |
ISSN 1534-7362 |
Limits of lightness identification for real objects under natural viewing conditions
Rocco Robilotto |
SUNY College of Optometry, New York, NY, USA |
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Qasim Zaidi |
SUNY College of Optometry, New York, NY, USA |
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Abstract
We examined whether observers veridically perceive
the reflectances of real objects under natural viewing conditions. A new
forced-choice paradigm was used to measure observers’ abilities to
identify (not match) the reflectance of randomly crumpled gray papers across two
levels of illumination, and also to simultaneously measure brightness
discrimination thresholds for the same objects. Accuracy of lightness
identification differed qualitatively among observers. By explicitly
manipulating observer strategies, we show that when observers use brightness
dissimilarity, their performance is similar to lightness identification. A
brightness adaptation model simulates how instead of extracting lightness,
observers can rely on perceived relative brightness to achieve the measured
degrees of lightness identification.
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