Figure 2.

(a) The spectrum reflected from flowers and green vegetation changes under changing illumination, e.g. (b) sun and shady spots, and leads to (c) changes in achromatic contrast that make object recognition difficult (black bars, shadow; white bars, sun). However, (d) even in dichromatic (but more obvious in trichromatic) colour space, all colours shift in the same direction. With colour constancy, colour shifts become even smaller (adapted from Kelber & Roth 2006). (d,e) Filled coloured circles show colour loci of objects in sunny spots, and crosses show colour loci of objects in the shade. For details of colour space diagrams, see figure 1.