Effect of chromatic contrast on stimulus brightness

Abstract

The effect of annuli of different wavelengths on the brightness of a chromatic stimulus was assessed by two different methods of measuring brightness, flicker photometry and direct brightness matching to an achromatic stimulus. With flicker photometry, annulus wavelength did not differentially affect stimulus brightness for different test wavelengths, but with direct brightness matches, annulus wavelengths that were the same as or similar to test stimulus wavelengths tended to affect the perceived brightness differently from annulus wavelengths that were dissimilar. These results suggest that, even when highly chromatic stimuli are used, lateral interactions that occur within the chromatic mechanisms do not affect the response in the achromatic mechanism. They also show that the evaluation of lateral interactions with chromatic stimuli depends on the response criterion used to assess those lateral effects and also add to the evidence that stimulus brightness includes chromatic activity as well as achromatic activity, depending on the method used to evaluate brightness.