Interpolation of illuminant cues across scenes with light fields induced by a mixture of a proximal and a collimated light source M Kim, L Maloney |
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Vision and Decision Laboratory, New York University, NY, United States
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| We examined how the visual system combines information from distant parts of the scene to estimate and discount the local light field. We rendered scenes with two bumpy rectangular grey surfaces separated by a gap. The scene was lit by a yellow proximal source (simulated distance: 1.15m) and a blue collimated source placed to the left and right of the observer respectively. The light impinging on a surface patch depended on the orientation of the patch to both sources and its location with respect to the yellow source. On each trial, a briefly flashed test surface patch (750ms) appeared at any of three locations within the gap, oriented at any of seven azimuths. Participants made forced-choice judgments of the yellow-blue balance of the test patch as we varied its yellow-blue chromaticity (staircase). We estimated their indifference points for each of the location-orientation conditions and compared human performance to that of an ideal observer discounting the light field. Five of seven participants correctly discounted the effect of changes in surface orientation. All participants failed to account for the effect of the proximal source as the target changed position suggesting that the visual system does not correctly discount for proximal illuminants. |
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