Abstract

Perceived contrast of the sum of a vertical and a horizontal grating of the same spatial frequency and contrast was estimated at threshold and suprathreshold contrast levels. The gratings with circular apertures and equiluminous surrounds were generated using computer graphics. Contrast thresholds were estimated by a two-alternative forced-choice method. Above threshold, contrast perception was studied using contrast matching. The contrast of a single component grating was matched with the perceived contrast of the two-component grating. At threshold, there was hardly any summation of the two grating components, as has been previously reported. However, above threshold there was summation: The perceived contrasts of the single component and the vertical-plus-horizontal gratings were equal when their rms contrasts (the standard deviation of the contrast waveform) were equal.

© 1989 Optical Society of America