ABSTRACT
In this chapter, the authors begin by considering relatively early stages of visual processing which furnish descriptions of the three-dimensional layout of the visual world from the observer’s point of view. The sensitivity of the human visual system to different spatial frequencies is most often studied by measuring how much “contrast” between the dark and light stripes of a pattern is needed for the pattern to be seen as “striped” rather than uniform in intensity. Garner’s distinctions between features, dimensions, and configurations give us some clear directions for considering the processing of two-dimensional patterns such as geometric shapes and alphanumeric characters. Land and McCann suggested that the visual system could recover “true” reflectances despite variations in illumination by ignoring any gradual changes in intensity across an image and attributing abrupt ones to reflectance changes from one surface patch to another.
