Lightness in a Flash: Effect of Exposure Time on Lightness Perception.

Sae Kaneko,Alan Gilchrist

doi:10.1177/2041669520983830

Sae Kaneko, Alan Gilchrist

Open Access

https://doi.org/10.1177/2041669520983830

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Abstract

A gray target can appear lighter or darker depending on its surrounding spatial context. We examined the effect of exposure time on three such examples (simultaneous lightness contrast, dungeon illusion, and the two-room arrangement), finding very different results with exposure time as brief as 15 ms: the simultaneous lightness contrast was much stronger, the effect of the dungeon illusion was reversed, and the lightness difference between the two isoluminant patches in the two-room arrangement disappeared. These suggest that local luminance ratios dominate lightness perception in a brief flash.

Highlights

A gray target can appear lighter or darker depending on its surrounding spatial context
In Bressan’s (2001) dungeon illusion (Figure 1C), two identical gray patches are locally surrounded by white and black but the one surrounded by black looks darker, not lighter; in other words, the illusory effect is opposite to the simultaneous lightness contrast
Kaneko and Murakami (2012) demonstrated that the simultaneous contrast illusion is much stronger when the stimulus duration is 10 ms compared to 500 ms. They showed that a spatial gap between the target and the background greatly reduced the illusion when the duration was 10 ms, but not when the duration was 500 ms. These results seem to indicate that lightness perception does vary with duration and the role of adjacent luminance ratio is much larger in a brief flash

Summary

Introduction

A gray target can appear lighter or darker depending on its surrounding spatial context. Wallach (1948) claimed that lightness perception was determined by the luminance ratio between a target and its immediate background. In Bressan’s (2001) dungeon illusion (Figure 1C), two identical gray patches are locally surrounded by white and black but the one surrounded by black looks darker, not lighter; in other words, the illusory effect is opposite to the simultaneous lightness contrast.

Results

Conclusion