Calculating lightnesses in a single depth plane

Abstract

The experiments in this paper demonstrate that ‘‘Early Vision’’ mechanisms can account for the appearance of three ‘‘Diamond Wall’’ demonstrations, without reliance on apparent illumination, transparency, apparent depth, and junctions. The first set (Section 2) demonstrates that simultaneous contrast and the Katz– Albers effect can explain the appearance of a Diamond Wall display. The second set (Section 3) reviews the ‘‘Straight Edge’’ experiments designed to show changes in lightnesses consistent with perceived illumination. These experiments showed that very-low-spatialfrequency sampling causes both these effects, and White’s effect. The third set (Section 4) applies complex Early Vision models to images associated with the ‘‘High Vision’’ lightness hypotheses. The argument is that flat displays, which are perceived as flat, require a quite complex visual mechanism just to account for the properties of flat lightnesses. Any experimental verification of the existence of High Vision lightness mechanisms should be tested first with realistic complex Early Vision models. The results show that Early Vision mechanisms can account for appearances in Diamond Wall experiments. If Early Vision mechanisms can explain these results, then these experiments cannot be used as evidence for the existence of High Vision mechanisms.