How Colours Appear at the Periphery

Let us stand in front of a uniformly white paper surface so that as much of the retina as possible is stimulated by the light reflected from it. Almost the entire visual field is then filled with white, and we can say with assurance that the colour has approximately the same brightness throughout its extent. Yet in spite of this equality in brightness of the central and peripheral parts of the surface, these differ from each other in a specific way. The insistence of the quality white decreases toward the peripheral parts, and finally reaches zero, i.e., the colour vanishes. ¹ Thus we see side by side in the visual field a series of different degrees of insistence of the same colour. There is a certain relationship between a colour in reduced illumination and central vision, and the same colour in normal illumination and peripheral vision. The two colour-impressions differ, however, in various respects. Different degrees of pronouncedness of a colour appear only in different intensities of illumination of the visual field. On the other hand, different degrees of insistence of a colour may appear side by side in a visual field of uniformly intense illumination. Indeed, we may even note such differences in film colours, to which we cannot ascribe illumination in the same sense as to surface colours. To observe different degrees of insistence of a film colour, we may simply look at the uniform colour of the sky. We might perhaps say that peripheral colours have less intensity, even though we have rejected this term in the case of colours presented in low intensity of illumination.