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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.
A light bulb is suspended in the center of the cylinder with the rotation speed making light emanate from the holes at a consistently pulsating frequency range of 8–13 flickers per second. It is meant to be looked at through closed eyelids, upon which moving yantra-like mandala visual patterns emerge, and an alpha wave mental state is induced.
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.
Flicker is however a directly visible effect resulting from light modulations at relatively low modulation frequencies, typically below 80 Hz, whereas stroboscopic effect in common (residential) applications may become visible if light modulations are present with modulation frequencies, typically above 80 Hz.
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 .
The distortion and the flicker caused by the rotating slits are not seen in most phénakisticope animations now found online (for instance the GIF animation on this page). These are usually animations created with software.
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.
The requirements of a flicker measurement equipment are defined in the international electro-technical standard IEC 61000-4-15. [2]A flickermeter is composed of several function blocks which simulate a 230 V/60 W or a 120 V/60 W incandescent lamp (reference lamp) and the human perception system (eye-brain model).