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Temporal light artefacts (TLAs) are undesired effects in the visual perception of a human observer induced by temporal light modulations. Two well-known examples of such unwanted effects are flicker and stroboscopic effect. Flicker is a directly visible light modulation at relatively low frequencies (< 80 Hz) and small intensity modulation levels.
The flicker fusion threshold, also known as critical flicker frequency or flicker fusion rate, is the frequency at which a flickering light appears steady to the average human observer. It is a concept studied in vision science , more specifically in the psychophysics of visual perception .
In visual perception, flicker is a human-visible change in luminance of an illuminated surface or light source which can be due to fluctuations of the light source itself, or due to external causes such as due to rapid fluctuations in the voltage of the power supply (power-line flicker) or incompatibility with an external dimmer.
Up to about 80 Hertz or the flicker fusion threshold it is called visible flicker. From about 80 Hertz to 2000 Hertz it is called the stroboscopic effect (this article). Overlapping in frequency, but from 80 Hertz up to about 6500 Hertz a third effect exists called the phantom array effect or the ghosting effect , an optical phenomenon caused ...
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The flicker of a CRT monitor can cause various symptoms in those sensitive to it such as eye strain, headaches [9] in migraine sufferers, and seizures in epileptics. [10]As the flicker is most clearly seen at the edge of our vision there is no obvious risk in using a CRT, but prolonged use can cause a sort of retinal shock where the flickering is seen even when looking away from the monitor.
Image credits: Green____cat Cyber and media psychologist Mayra Ruiz-McPherson , PhD(c), MA, MFA, explains that broadly speaking, "negative news" can describe two kinds of events and happenings.
Impressions of several natural phenomena and the principles of some optical toys have been attributed to persistence of vision. In 1768, Patrick D'Arcy recognised the effect in "the luminous ring that we see by turning a torch quickly, the fire wheels in the fireworks, the flattened spindle shape we see in a vibrating cord, the continuous circle we see in a cogwheel that turns with speed". [8]