The Luminous Efficiency of Rays Entering the Eye Pupil at Different Points (Illustrations and Annotations)

The assumption that the apparent brightness of an object is proportional to the pupil area is shown to be invalid, and measurements are described which give the relative luminous efficiencies of rays entering the pupil at different points. From these data the total efficiencies of eye pupils at different diameters are computed, and checked by direct measurement. Whether these variations are due to the eye media or originate in the retina itself is at present uncertain; the latter seems more probable.