Precise assessment of the mean effective luminance of texture patches--an approach based on reverse-phi motion

In studying the response of mechanisms to contrast-defined texture stimuli, it is critical that the average effective luminance of these textures be equal to that of the background, to minimize net luminance-based signals. We present an efficient and accurate technique for constructing such equiluminant textures to isolate contrast-sensitive mechanisms for investigating their properties. The technique is based on the reverse-phi motion phenomenon, and the resulting settings agree closely with those obtained by photometric means for the class of textures studied. The method also allows one to explore the properties of contrast- and luminance-driven motion mechanisms and, in particular, to evaluate the contribution of putative second-order mechanisms to the motion percept. Results of applying the method are presented, and its advantages over the minimum-flicker and minimum-motion techniques are discussed.