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Sae Kaneko, Alan Gilchrist; Lightness perception in a flash. Journal of Vision 2020;20(11):954. doi: https://doi.org/10.1167/jov.20.11.954.
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A gray square placed on a black background appears lighter than the same square placed on a white background (simultaneous lightness contrast). Kaneko and Murakami (2012) showed that the simultaneous contrast was stronger when the stimulus duration was 10 ms compared to 500 ms. In this study we tested the effect of exposure time on lightness perception in scenes more complex than the stimuli used by Kaneko & Murakami (2012). Subjects viewed three kinds of display: (1) simultaneous lightness contrast, (2) Bressan’s dungeon illusion (Bressan, 2001), and (3) Gilchrist’s two-room arrangement (Gilchrist, 1977), and made matches to the target squares using a Munsell chart. Viewing duration was either long (unlimited) or short (~15 ms using a camera shutter). We found that with short exposure, the simultaneous contrast illusion was four times larger than with long exposure, confirming the early report by Kaneko and Murakami (2012). The dungeon illusion, a reverse-contrast illusion at long exposure, reversed direction, becoming a conventional contrast illusion at short exposure. In Gilchrist’s two-room arrangement, at long exposure, the target appeared black in the far lighted plane and light gray in the near shadowed plane. But this difference was greatly reduced, or eliminated at short exposure, suggesting the absence of a depth effect. While the long exposure results are consistent with anchoring theory (Gilchrist, 2006) and its emphasis on depth and grouping factors, the short exposure results are consistent with Wallach’s (1948) ratio theory. That is, targets are seen merely in relation to their retinal surround.
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