Document Detail

Matching illumination of solid objects.
MedLine Citation:
PMID:  17672433     Owner:  NLM     Status:  MEDLINE    
The appearance of objects is determined by their surface reflectance and roughness and by the light field. Conversely, human observers might derive properties of the light field from the appearance of objects. The inverse problem has no unique solution, so perceptual interactions between reflectance, roughness, and lightfield are to be expected. In two separate experiments, we tested whether observers are able to match the illumination of spheres under collimated illumination only (matching of illumination direction) and under more or less diffuse illumination (matching of illumination direction and directedness of the beam). We found that observers are quite able to match collimated illumination directions of two rendered Lambertian spheres. Matching of the collimated beam directions of a Lambertian sphere and that of a real object with arbitrary reflectance and roughness properties resulted in similar results for the azimuthal angle, but in higher variance for the polar angle. Translucent objects and a tennis ball were found to be systematic outliers. If the directedness of the beam was also varied, the direction settings showed larger variance for more diffuse illumination. The directedness settings showed an overall quite large variance and, interestingly, interacted with the polar angle settings. We discuss possible photometrical mechanisms behind these effects.
Sylvia C Pont; Jan J Koenderink
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Perception & psychophysics     Volume:  69     ISSN:  0031-5117     ISO Abbreviation:  Percept Psychophys     Publication Date:  2007 Apr 
Date Detail:
Created Date:  2007-08-03     Completed Date:  2007-08-27     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0200445     Medline TA:  Percept Psychophys     Country:  United States    
Other Details:
Languages:  eng     Pagination:  459-68     Citation Subset:  IM    
Helmholtz Institute, Department of Physics and Astronomy, Utrecht University, Utrecht, The Netherlands.
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MeSH Terms
Visual Perception*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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