Visual adaptation produced by gratings with no brightness contrast

Abstract

A STRIPED grating is more difficult to see after prolonged viewing of a similar grating^1,2. Similarly, the contrast threshold is elevated when a test grating is briefly presented superimposed on a continuously viewed grating^3,4. Here we show that the threshold is raised by gratings that have no brightness difference between alternate stripes, but only a hue difference. We measured luminance modulation thresholds for seeing a yellow grating superimposed on a background of interdigitated red and green stripes. We varied the relative luminances of the red and green stripes while holding the sum of their luminances constant. Thus we could be certain that for some luminance ratio, the red and green stripes must have had the same subjective or effective brightness for the observer. Nevertheless, we found that for all ratios of red-to-green luminance the contrast threshold for the test grating was higher than that obtained in several control conditions (including backgrounds with the same colours and configuration but perpendicular to the test grating, and uniform backgrounds with the same mean spectral composition).