The psychophysics of spatial sampling

Abstract

In this paper, we study the physical and psychophysical effects of digital sampling. In particular, we study how spatial sampling (the geometry of the pixel array) and luminance sampling (the distribution of gray levels) affect the image and its perception. Taking the Thin-Film Transistor Liquid Crystal Display (TFT/LCD) as our model, we have simulated four candidate pixel geometries on a color graphics display. We have made psychophysical measurements of visual detectability, reaction time, and rated quality as a function of pixel geometry and grayscale. Our major findings are that (1) the spatial geometry of the sampling array exerts a major influence on visual performance, (2) for suprathreshold judgments of image quality, asymptotic performance is reached with as few as 2-3 bits of grayscale, and (3) the effect of grayscale on performance depends on exposure duration. © 1988, SPIE.