The Effect of a Peripheral Glare Source upon the Apparent Brightness of an Object

The decrease in perceived brightness of a foveal test object produced by a peripheral glare source can be accounted for in terms of a veiling luminance produced by stray light falling on the fovea. The same effect can be produced by an artificial patch of veiling luminance superimposed on the test object. The effect of increasing the angle between the glare source and the test object is equivalent to reducing the brightness of the glare source in accordance with the stray light hypothesis. The measured amount of veiling luminance conforms to that found by previous investigators. The changes in brightness that occur immediately following the onset of a peripheral glare source as well as the changes which occur following removal of the glare source can all be accounted for in terms of the veiling luminance produced by stray light falling on the fovea.