flicker

Flicker, in the context of vision, refers to the sensation of rapid fluctuations in brightness when a light source is repeatedly interrupted. This phenomenon is particularly noticeable at lower light levels, where as few as four flashes per second can be perceived as flickering. As the intensity of light increases, so does the speed at which these flashes must occur to be perceived as continuous. This threshold speed is known as the critical fusion frequency. At high light levels, this can be as high as 60 flashes per second. This difference in perception between rod and cone vision is likely due to the eye's ability to rapidly inhibit activity in cones, allowing them to respond to subsequent stimuli more quickly than rods.1