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Flicker (light)
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.
Twinkling, also called scintillation, is a generic term for variations in apparent brightness, colour, or position of a distant luminous object viewed through a medium.
Flicker exists for other organisms having different perceptual thresholds.
Light meters and image sensors can potentially detect flicker at much higher frequency bands than human vision. Shutter speeds used in motion photography can interact with high frequency flicker to produce visual artifacts in the captured imagery that betray flicker that would not otherwise be noted.
The spectral sensitivity of the human eye to flicker depends upon the mode of visual perception. Due to the flicker fusion threshold of foveal vision, steady vision can rarely detect flicker above 90 Hz, whereas flicker can be perceived during visual saccades up to or beyond 1 kHz.
Flicker due to mechanical factors such as AC line frequency (typically 50 or 60 Hz) will have a stable frequency structure, whereas the flicker of a damp or failing light bulb will often have a chaotic or erratic frequency structure.
Temporal light modulation (TLM) is a slightly broader concept defined by the International Commission on Illumination (CIE) as fluctuation in luminous quantity or spectral distribution of light with respect to time. The effect is typically connected to lighting products such as lamps and luminaires where the light is modulated in order to provide some functionality, such as dimming or color change. TLM can cause temporal light artifacts (TLA) such as the stroboscopic effect or phantom array effect. TLM has been linked to headache and migraine, and in rare cases epileptic seizures.
Various scientific committees have assessed the potential health, performance and safety-related aspects resulting from TLMs, including light flicker. Adverse effects of flicker include annoyance, reduced task performance, visual fatigue, headache and epileptic attack by photosensitive persons. The visibility aspects of flicker are given in a technical note of CIE; see CIE TN 006:2016. In general, undesired effects in the visual perception of a human observer induced by light intensity fluctuations are called temporal light artefacts (TLAs).
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Flicker (light)
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.
Twinkling, also called scintillation, is a generic term for variations in apparent brightness, colour, or position of a distant luminous object viewed through a medium.
Flicker exists for other organisms having different perceptual thresholds.
Light meters and image sensors can potentially detect flicker at much higher frequency bands than human vision. Shutter speeds used in motion photography can interact with high frequency flicker to produce visual artifacts in the captured imagery that betray flicker that would not otherwise be noted.
The spectral sensitivity of the human eye to flicker depends upon the mode of visual perception. Due to the flicker fusion threshold of foveal vision, steady vision can rarely detect flicker above 90 Hz, whereas flicker can be perceived during visual saccades up to or beyond 1 kHz.
Flicker due to mechanical factors such as AC line frequency (typically 50 or 60 Hz) will have a stable frequency structure, whereas the flicker of a damp or failing light bulb will often have a chaotic or erratic frequency structure.
Temporal light modulation (TLM) is a slightly broader concept defined by the International Commission on Illumination (CIE) as fluctuation in luminous quantity or spectral distribution of light with respect to time. The effect is typically connected to lighting products such as lamps and luminaires where the light is modulated in order to provide some functionality, such as dimming or color change. TLM can cause temporal light artifacts (TLA) such as the stroboscopic effect or phantom array effect. TLM has been linked to headache and migraine, and in rare cases epileptic seizures.
Various scientific committees have assessed the potential health, performance and safety-related aspects resulting from TLMs, including light flicker. Adverse effects of flicker include annoyance, reduced task performance, visual fatigue, headache and epileptic attack by photosensitive persons. The visibility aspects of flicker are given in a technical note of CIE; see CIE TN 006:2016. In general, undesired effects in the visual perception of a human observer induced by light intensity fluctuations are called temporal light artefacts (TLAs).