The Perception of Lightness in 3-D Curved Objects

Abstract

Lightness constancy requires the visual system to somehow "parse" the input scene into illumination and reflectance components. Experiments on the perception of lightness for 3-D curved objects show that human observers are able to perform such a decomposition for some scenes but not for others. Lightness constancy was quite good when a rich local gray level context was provided. Deviations occurred when both illumination and reflectance changed along the surface of the objects. Does the perception of a 3-D surface and illuminant layout help calibrate lightness judgements? Our results showed a small but consistent improvement between lightness matches on ellipsoid shapes compared to flat rectangle shapes under similar illumination conditions. Illumination change over 3-D forms is therefore taken into account in lightness perception.