Where does flicker collide?

In visual psychophysics, flicker is a periodically modulated light stimulus, and the critical flicker fusion frequency is the rate above which an observer can no longer see the modulation and the light appears steadily lit. The visual system behaves as a temporal filter whose sensitivity falls off at high frequencies, so fusion depends on the modulation depth and the mean luminance. De Lange charted these attenuation characteristics for the human fovea. The referent is a property of temporal vision, unrelated to a mains voltage swing or a woodpecker.[1]

Unit

The critical fusion frequency, in hertz, at which flicker disappears

Recovery means

Not applicable

Measured by

Measured as the critical flicker fusion frequency across modulation depth and mean luminance

In power quality, flicker is the perceptible fluctuation in lamp light output caused by rapid variations in the supply voltage, typically from fluctuating loads such as arc furnaces, welders, or large motor starts. Because the nuisance is ultimately a visual one, it is quantified by perceptibility indices, the short-term and long-term flicker severity, that weight voltage fluctuations by how the eye and a reference lamp respond to them. The referent is a power-system disturbance, distinct from the perceptual threshold it borrows its name from and from the bird.[2]

Unit

The short-term and long-term flicker severity indices

Recovery means

Not applicable

Measured by

Quantified by flickermeter severity indices derived from the supply-voltage fluctuation