Abstract

We previously reported (OSA, 1991; ARVO, 1992) that perceived brightness of an achromatic surface is influenced by information about the illuminant derived from perceptually coplanar but retinally noncontiguous surfaces. A 6:1 luminance range on a CRT screen simulated the surface reflectances of a single Mondrian. Corresponding spatial locations in a second Mondrian were assigned luminances that were one-fifth that of the first Mondrian. This created the appearance of two Mondrians with identical reflectances, but different illuminations. When viewed through a haploscope each Mondrian was perceived in a separate stereoscopic depth plane. The test appeared in either the depth plane of the far, dimly illuminated Mondrian or the depth plane of the near, brightly illuminated Mondrian. The previous results confound changes of reflectance and illumination. We obtained lightness judgments by using the same stimuli to isolate perceived reflectance. The results show that brightness of the test changed with depth, but not lightness. This supports the claim that brightness measures are due to perceived illumination differences across depth planes.

© 1992 Optical Society of America