Abstract

Colour difference thresholds reflect the sensitivity of the channels involved in chromatic discrimination and have been measured elegantly by MacAdam for several directions of modulation in the CIE (x,y) - chromaticity diagram from estimates of standard deviation associated with successive colour matches (MacAdam, 1942). The extent of isochromatic regions, formally associated with the direction of colour confusion lines (Pitt, 1935, Wright, 1952) can in principle be mapped out in colour discrimination experiments although in practice the luminance contrast of the test pattern as seen by colour deficient observers makes such measurements difficult to carry out. Mollon and Reffin (1989) have developed a test which overcomes largely these difficulties by following the techniques described by Stilling (Stilling, 1877) which are based on the relative insensitivity of the visual system when required to judge luminance differences between spatially discountinuous target elements, presented on a dark background field and varying randomly in luminance. We have extended this approach and eliminated the need to use a dark background field by developing a Random, spatiotemporal Luminance Masking (RLM) technique. The method employs a matrix of spatially discrete elements which form part of the uniform background field and are equal in time-averaged luminance to that of the background.

© 1992 Optical Society of America