Effects of colour on perceived depth: Review of experiments and evalutaion of theories

A selective and evaluative review of experiments and theories dealing with the effect of colour on perceived depth is presented. It has long been known that equidistant objects that differ in colour may appear as if they are located at different distances. The present paper emphasizes the theoretical importance of distinguishing between monocular and binocular effects. There is at present no completely satisfactory explanation of the monocular effect but chromatic aberration seems to be a critical factor. The binocular effect (colour stereoscopy) is most probably due to disparity between differently coloured images on the retinae. The stereoscopic theories of Einthoven (1885) and Vos (1960, 1963, 1966) are discussed; available evidence favours the latter.