Fechner's Paradox

Fechner’s paradox occurs when you perceive that the brightness decreases when using both eyes as compared to using only one eye when looking through a dark filter. This is a result of binocular summation in which light is distributed to both eyes during binocular vision while light is concentrated on one eye in monocular vision. This is a surprising phenomenon since more light is received in binocular vision than in monocular vision. This was introduced by Gustav Fechner, a German philosopher, physicist, and experimental psychologist.