Fechner color

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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 stroboscopic lights when flashes are set at certain critical speeds. Rotating fan blades, particularly aluminium ones, can also demonstrate the effect ; as the fan accelerates or decelerates, the colours appear, drift, change and disappear. The stable running speed of the fan doesn't (normally) produce colours, suggesting that it's not an interference effect with the frequency of the illumination flicker.

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. 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)

[edit] External links

• Online Java demonstrations of Fechner color