When the illuminance of a scene increases, and its brightness rises above 10?? candela/m2, three effects are observed, similar to those observed with normal brightness increases:
First, foveal perception becomes as easy as peripheral perception;
Second, the color of the scene becomes noticeable, initially faint and then gradually intensifying;
Third, the relative brightness of objects of different colors changes, with the brightness of red increasing more than that of blue.
This third effect, known as the Purkinje phenomenon, is the result of changes in the contribution of rod and cone receptors to vision caused by changes in brightness within the intermediate range (10?? to 10?? candela/m2).