Editing Fechner color effect

{{Short description|Illusion of color}}
The '''Fechner color effect''' 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''').

[[Image:Benham's Disc.svg|thumb|A sample of a Benham's top ([[:File:Benham's disc (animated).gif|animated version]])]]
The effect is most commonly demonstrated with a device known as '''Benham's top''' (also called '''Benham's disk'''). When the top is spun, arcs of pale color are visible at different places on the disk that forms its upper surface. The effect can also be seen in [[stroboscope|stroboscopic lights]] when flashes are set at certain critical speeds. Rotating fan blades, particularly aluminum ones, can also demonstrate the effect; as the fan accelerates or decelerates, the colors appear, drift, change and disappear. The stable running speed of the fan does not (normally) produce colors, suggesting that it is not an interference effect with the frequency of the illumination flicker.

The effect was noted by [[Gustav Fechner]] and [[Hermann von Helmholtz]] and propagated to English-speakers through [[Charles Benham]]'s invention of his top. [[Florence Bagley|Florence Winger Bagley]] was one of the early investigators of this phenomenon.<ref name="Fechners_colors_1902">{{cite journal |last1=Bagley |first1=Florence Winger |title=An investigation of Fechner's colors |journal=American Journal of Psychology |date=1902 |volume=14 |issue=4 |pages=488–525 |doi=10.2307/1412440 |jstor=1412440 }}</ref>

The [[perception|perceptual]] mechanism of Fechner color is not entirely understood.<ref>{{cite journal |last1=Nishiyama |first1=Yutaka |title=A Dynamic Interference Model for Benham's Top |journal=Journal of Osaka University of Economics |date=May 2023 |volume=74 |issue=1 |page=99 |arxiv=2303.04624 |access-date=10 January 2024 |url=https://www.jstage.jst.go.jp/article/keidaironshu/74/1/74_99/_article/-char/en}}</ref> 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.{{citation needed|date=January 2024}} Or, more specifically, that the latencies of the center and the surrounding mechanisms differ for the different types of color-specific ganglion cells.{{citation needed|date=January 2024}}

The phenomenon originates from neural activity in the [[retina]] and spatial interactions in the [[primary visual cortex]], which plays a role in encoding low-level image features, such as edges and spatiotemporal frequency components.<ref>{{cite journal |author1=von Campenhausen C. |author2=Schramme J. |title=100 years of Benham's top in colour science |journal=Perception |volume=24 |issue=6 |year=1995 |pages=695–717 |doi=10.1068/p240695 |pmid=7478909 |s2cid=45743116 }}</ref> Research indicates that the blue–yellow [[opponent process]] accounts for all the different PIFCs.<ref>{{cite journal |author=Schramme J. |title=Changes in pattern induced flicker colors are mediated by the blue/yellow opponent process |journal=Vision Research |volume=32 |issue=11 |year=1992 |pages=2129–2134 |doi=10.1016/0042-6989(92)90074-S |pmid=1304090 |s2cid=27439228 }}</ref>

Research has been done into the use of Benham's top and other PIFCs as diagnostic tools for diseases of the eye and the visual track. It has shown particular promise in detecting [[optic neuritis]].<ref>{{cite journal |author1=Pilz J. |author2=Marre E. |title=Pattern-induced flicker colors. An ophthalmologic examination method |lang=de |journal=Ophthalmologe |volume=90 |issue=2 |year=1993 |pages=148–154 |pmid=8490297}}</ref>

== Benham's top ==
{{unreferenced section|date=January 2024}}
'''Benham's top''' is named after the English newspaper-man, amateur scientist, and toymaker [[Charles Benham]], who in 1895 sold a [[Spinning top|top]] painted with the pattern shown. Benham was inspired to propagate the Fechner color effect through his top after his correspondence with [[Gustav Fechner|Gustav Theodor Fechner]], who had observed and demonstrated the said effect. Benham's top made it possible for speakers of the English language to learn of the Fechner color effect, about which Fechner's original reports were written in German.

==See also==
* [[Newton disc]]

==References==
{{Reflist}}

==External links==
{{commons category|Benham's top}}
* [http://dogfeathers.com/java/fechner.html Online Java demonstrations of Fechner color]
* [http://faculty.washington.edu/chudler/benham.html Benham's Disk]
* [http://www.michaelbach.de/ot/col_benham/index.html Interactive version] ({{Webarchive|url=https://web.archive.org/web/20211110023722/https://michaelbach.de/ot/col_benham/index.html |date=2021-11-10 }}) by [[Michael Bach (vision scientist)|Michael Bach]]
* [https://michaelbach.de/ot/col-Benham2/index.html A more convincing interactive version from Michael Bach]

{{DEFAULTSORT:Fechner Color}}
[[Category:Optical illusions]]
[[Category:Color]]