Colour associated with Scotopic Vision

Abstract

IT is usually asserted that scotopic vision, that which is associated with the rods, gives no sensation of colour. Nevertheless it has also been suggested that under photopic conditions the rods may function as the blue-sensitive receptors. In support of this idea it is cited that: (1) the fovea which is rod-free also lacks blue-sensitive receptors; (2) rhodopsin admixed with a large proportion of its own product of bleaching, visual yellow, could have a resultant activity – wave-length relationship similar to that expected for the blue-sensitive receptor; (3) moonlit scenes seem somewhat bluish although an analysis of the light shows it to have a lower colour temperature than sunlight.