# Flicker fusion frequency

Flicker fusion frequency depending on age

The flicker fusion frequency ( CFF ), also Flimmerfusionsfrequenz or critical flicker frequency ( English critical flicker frequency called CFF), is "the frequency at which a sequence of light irritation is perceived as a continuous light." In case of incomplete fusion occurs flicker on. A minimum time is required for the chemical processes in the retina of the eye that are triggered by light stimulation and lead to excitation. If the time interval between individual stimuli is shorter than this minimum time, then these stimuli cannot be perceived as periodic and cannot be distinguished from a stimulus that lasts evenly; in this case the eye's temporal resolution is exceeded.

The cut-off frequency at which periodically recurring stimuli are perceived as a stimulus is called the "flicker fusion frequency" and lies between 22  Hz and 90 Hz. It depends on the strength of the stimuli, the state of adaptation of the retina and the general level of activation of the recipient. Attempts have been made to use the flicker fusion frequency as a parameter for measuring fatigue conditions. It also depends on the size of the exposed retinal area, the luminance and the wavelength of the light.

In humans it is at low light intensity (= scotopic vision / rods ) at 22 Hz to 25 Hz. At higher light intensities, photopic vision is possible and the cones on the retina are additionally stimulated. The human flicker fusion frequency then increases with the logarithm of the light intensity and depending on the area distribution of the light intensity up to 90 Hertz . It follows the Ferry-Porter law with a = 12 Hz, b = 33 Hz and Lm as the mean luminance according to Talbot's law . ${\ displaystyle f _ {\ text {v}} = a \ cdot \ log L _ {\ text {m}} + b}$

In the case of small stimulating areas on the fovea , the spot of sharpest vision, the FVF increases linearly with the logarithm of the luminance at all wavelengths. In the case of stimulation outside the fovea and at the edge of the visual field, a two-legged curve results, whereby the section obtained with low luminance (low FVF) only occurs in the edge of the retina and with stimuli (white and blue) that are effective in twilight vision. It is also absent in the irritation of the fovea. This frequency depends on the anatomy of the visual apparatus, for example the fine structure of the receptor cells of the eye and the subsequent neuronal processing. In contrast, a flicker fusion frequency of 240 Hz was measured in the completely differently built compound eye of the fly.

## Trivia

Some people have high FVF; For example, the painters da Vinci and Hokusai correctly drew the turbulence of water that is otherwise invisible to the naked eye and the angle of attack of four-winged insects (Hokusai: mayfly , da Vinci: dragonfly ).

## Individual evidence

1. E. Biecker, I. Hausdörfer u. a .: The critical flicker frequency as a marker of minimal hepatic encephalopathy in patients before and after TIPS application. In: Zeitschrift für Gastroenterologie , 47, 2009, doi: 10.1055 / s-0029-1241384 .
2. ^ Holger Luczak: Ergonomics . 2., completely reworked. Edition. Springer, Berlin [a. a.] 1998, ISBN 3-540-59138-9
3. Yves Galifret: Visual persistence and cinema? In: Comptes Rendus Biologies. , Volume 329, Nos. 5-6, 2006, pp. 369-385, PMID 16731495 .
4. ^ A b c Schmidt, Lang, Heckmann: Physiology of humans with pathophysiology . 31st edition. Springer Verlag, Heidelberg 2010, ISBN 978-3-642-01650-9 , p. 366
5. ^ Heinz Schmidtke, Rainer Bernotat, Wolf Müller-Limmroth: Ergonomics . 3., rework. and exp. Ed.
6. Hans-Jürgen Hentschel (Ed.): Light and lighting . 5., rework. and exp. Aufl. Hüthig, Heidelberg 2002
7. ^ David S. Thaler: Evidence for extraordinary visual acuity in Leonardo's comment on a dragonfly. In: Actes du Colloque International d'Amboise: Leonardo de Vinci, Anatomiste. Pionnier de l'Anatomie comparée, de la Biomécanique, de la Bionique et de la Physiognomonie. CNRS editions, Paris, in press. Henry de Lumley (ed.), Accessed June 27, 2020 .