Dark-Adaptation and Night Vision

Publisher Summary This chapter discusses experiments in which the dark-adaptation and night vision of human eye are measured. The first experiments on the capacity of the eye to increase in sensitivity during a stay in the dark appear to have been made by Aubert. Both the rod-free fovea and the periphery can dark-adapt, but the dark adaptation of the cones is more rapid than that of the rods, so that for a time it was erroneously believed that only the rods were capable of dark-adaptation. In the case of the fully dark-adapted periphery both rods and cones become active when submitted to intensities above the cone threshold, the rods are most probably out of action over the extent of time covered by the cone curve of the dark-adaptation experiments. Duration and shape of the two main branches of the dark-adaptation curve are greatly influenced by the conditions of light-adaptation and by the characteristics of the test stimulus.