On negative after-images, and their relation to certain other visual phenomena

Abstract

In a former communication I described a curious phenomenon due to the formation of negative after-images following brief retinal excitation after a period of darkness. The effect is conveniently demonstrated by tins aid of a disc, partly black and partly white, having an open sector, as shown in fig. 1. If such a disc is caused to turn five or six times in a second, while its surface is strongly illuminated, a coloured object placed behind it and viewed intermittently through the open sector, generally appears to assume an entirely different hue, which is approximately complementary to the true colour of the object: a piece of red ribbon, for example, is seen as greenish-blue and a green one as pink.