Illusory lightness in the Delboeuf figure.
Lucia Zanuttini1, Olga Daneyko
1Department of Philosophy, University of Udine, Italy. lucia.zanuttini@uniud.it
Perceptual and Motor Skills
|February 16, 2011
Summary
The size of surrounding circles influences perceived lightness. A white disk appears lighter within smaller surrounding circles, demonstrating a contrast effect in visual perception.
Area of Science:
- Visual Perception
- Psychophysics
- Color Science
Background:
- The Delboeuf figure illustrates simultaneous contrast, where the perceived lightness of a central area is affected by the luminance of its surround.
- Previous research has explored contrast effects, but precise quantification of this specific visual phenomenon is ongoing.
Purpose of the Study:
- To quantify the perceived lightness change of a central white disk within concentric circles of varying sizes.
- To measure the magnitude of the Delboeuf effect under controlled conditions.
Main Methods:
- Utilizing a display similar to the Delboeuf figure with a white disk inside concentric circles.
- Recruiting 20 observers (10 women, 10 men, ages 19-26) for psychophysical measurements.
- Measuring luminance decrements required to match the perceived lightness of the central disk across different background conditions.
Main Results:
- A white disk appeared lighter when enclosed by a smaller concentric circle compared to a larger one.
- Significant luminance decrements were required to match perceived lightness, averaging 9.13%, 10.33%, and 10.46% across three grey backgrounds.
- These results indicate a substantial contrast effect influencing lightness perception.
Conclusions:
- The size of the surrounding context significantly modulates the perceived lightness of an object.
- The Delboeuf effect, a form of simultaneous contrast, is reliably demonstrated and quantifiable.
- Findings contribute to understanding the complex mechanisms of human visual perception and lightness constancy.
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