<title>Calculating the lightness of areas in a single plane</title>

Abstract

This paper studies two different 'Diamond Wall' experiments. It demonstrates that 'Early Vision' explanations are possible, without reliance on apparent illumination, transparency, apparent depth and junctions. Grays ordinarily look darker on light backgrounds. Adelson showed that two rows of diamonds looked the same on different backgrounds when the diamond tips crossed into the other background. He added different gray tips, consistent with illumination changes, thus releasing the rest of the diamonds to no-longer looking the same. Grays on light backgrounds reverted to looking darker. New experiments show that the introduction of any edge along the light-dark background boundary releases the diamonds to look different in different surrounds. Whereas Adelson introduced diamond tips consistent with illumination, we used lines, dots, Cornsweet edges and non-consistent tips to release the diamonds to look different. Apparent illumination and apparent depth were not necessary because small abstract displays (one-quarter diamond) affected lightnesses the same as the complex displays. We apply complex 'Early Vision' models to images associated with 'High Vision' 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 flat 'Early Vision' models. The results show that different 'Early Vision' approaches account for these 'Diamond Wall' experiments. If 'Early Vision' mechanisms can account for the results, then these experiments cannot be used as evidence for the existence of 'High Vision' mechanisms.