Gray Haze Optical Illusion

Stare at the black dot for 20 or 30 seconds. Did anything change to lift that grayness, or was it just a shift in your mood?

See Another Random Optical Illusion

Explanation

This optical illusion works because the retina gradually changes sensitivity to adapt to the existing light conditions. Our eyes automatically adjust. This is what allows us to see in diverse light conditions, from bright sunlight to faint moonlight.