Fechner color

Fechner color is an illusion of color seen when looking at certain rapidly changing or moving black-and-white patterns. They are also called pattern induced flicker colors (PIFCs). Not everyone sees the same colors.

It is most commonly demonstrated with a device known as Benham's top. It can also be seen in stoboscopic lights when flashes are set at certain critical speeds. The effect was noted by Gustav Fechner and Hermann von Helmholtz. The perceptual mechanism of Fechner color is not entirely understood.

When the disk is spun, arcs of pale color are visible at different places on the disk. The phenomenon is not entirely understood. One possible reason people see colors may be that the color receptors in the human eye respond at different rates to red, green, and blue. Or, more specifically, that the latencies of the centre and the surrounding mechanisms differ for the different types of color-specific ganglion cells.

The phenomenon originates from neural activity in the retina and spatial interactions in the primary visual cortex, which processes pattern recognition. (von Campenhausen & Schramme, 1995) Research indicates that that the blue-yellow opponent process accounts for all the different PIFCs. (Schramme, 1992)

When the rotation is slowed sufficiently, there appears a series of black radii on a white background and these are known as Charpentier bands.