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SUMMARY:Specular surfaces improve colour constancy - Dr. Robert Lee (Linco
 ln)
DTSTART:20151126T130000Z
DTEND:20151126T140000Z
UID:TALK61090@talks.cam.ac.uk
CONTACT:John Mollon
DESCRIPTION:Changes in the surface reflectance of an object and changes in
  the spectral content of the illumination both change the spectral composi
 tion of light reaching our eyes\, but usually we do not have difficulty de
 termining which change occurred. We investigated how specular reflections 
 might allow an observer to distinguish changes in lighting and reflectance
  in scenes containing only one surface. Specular reflections make a surfac
 e look glossy and contain reflected light that has not been spectrally mod
 ified by the surface\, so could provide information about the illuminant. 
 Additionally\, there are spatio-chromatic changes that differ systematical
 ly for changes in lighting and reflectance\, and we investigate how observ
 ers extract information that is not available at any given instant. We pre
 sented hyperspectrally raytraced movies showing isolated objects undergoin
 g gradual illuminant and reflectance changes. Observers were able to disti
 nguish the two types of change at very low specularities (~1%). Performanc
 e was reduced\, but not extinguished\, when we distorted the images to wea
 ken some of the spatial or chromatic relationships. The highlights on low-
 gloss surfaces are heavily contaminated by surface colour so they do not a
 llow direct estimation of the illuminant. Yet the chromatic transitions un
 der gradual changes in lighting and reflectance are perceptually discrimin
 able.
LOCATION:Nick Mackintosh Seminar Room\, Department of Psychology\, Downing
  Site\, Cambridge
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