Colour induced stereopsis in images with achromatic information and only one other colour.

Based on a model of transverse chromatic aberration (TCA) of the eye and perceptual effects previously discussed by the same author, it was predicted that colour induced binocular depth perception (chromostereopsis) is possible from images containing red or blue along with achromatic information (grey and black); that the direction of the perceived depth from certain colours should differ for the same TCA conditions; and that a greater depth perception should be possible in a blue/achromatic image than a red/achromatic image. Results of TCA manipulations support all three predictions and demonstrate that colour induced depth effects can be perceived in images having only achromatic information and a single non-achromatic colour. It is argued that optical factors, image characteristics and perceptual factors all play an important role in colour depth effects under natural viewing conditions. Further, the possibility is raised that colour and texture patterns which produce colour depth effects have evolved within certain species for camouflage or other behavioural purposes.