Adelson’s “Corrugated Plaid”
Compare the top and bottom gray squares for their brightness. They appear (and,
indeed, physically are) equal. Moving the mouse over the image removes the red bars.
Now the squares appear in a different context, and lo and behold, they do not look
equal anymore.
Comment
When interpreted as a 3-dimensional scene, our visual system immediately estimates
a lighting vector and uses this to judge the property of the material.
The explanation is disputed by Todorovic (1997) [thanks to Mark E. McCourt for the
pointer]. However, I do not find his counter example (bottom left) completely convincing.
See next illusion for a stronger effect.
Source
Adelson EH (1993) Perceptual organization and the judgment of brightness. Science
262:2042–2044
New Demo from Adelson's site
Todorovic D (1997) Lightness and junctions. Percept 26:379–395
Created: 2002-06-13
Last update: 2013-10-04