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Journal of Vision -Parametric measurements of lightness in the cont... http://www.journalofvision.org/7/9/234/ 1 of 2 7/2/08 12:31 PM
 

Summary: Journal of Vision - Parametric measurements of lightness in the cont... http://www.journalofvision.org/7/9/234/
1 of 2 7/2/08 12:31 PM
Volume 7, Number 9, Abstract 234, Page 234a doi:10.1167/7.9.234 http://journalofvision.org/7/9/234/ ISSN 1534-7362
Parametric measurements of lightness in the context
of real illuminated objects
Sarah R. Allred Department of Psychology, University of Pennsylvania
David H. Brainard Department of Psychology, University of Pennsylvania
Abstract
Purpose: The visual system achieves partial lightness constancy across illumination
gradients and variations in object pose. What scene variables mediate this constancy?
Here we report parametric measurements of how the slant and reflectance of a
background surface affect the lightness of test spots seen against that surface. Methods:
Observers looked into an experimental chamber. Two spatially separated cards provided
the immediate backgrounds for a test and matching spot. The slant of the background
cards could be varied using computer-controlled rotating stages. Changes in the
reflectances of background cards were simulated with a hidden projector. Observers
compared the apparent lightness of simulated spots projected onto the background cards.
We held the slant and simulated reflectance of one background card fixed and varied the
slant and simulated reflectance of the other. We obtained matching curves which related
the luminance of a spot on the fixed background card to the luminance of a

  

Source: Allred, Sarah - Department of Psychology, University of Pennsylvania

 

Collections: Biology and Medicine