technical note of CIE, see CIE TN 006:2016 and in the thesis of Perz. Stroboscopic effects may also lead to unsafe situations in workplaces with fast moving or rotating machinery. If the frequency of fast rotating machinery or moving parts coincides with the frequency, or multiples of the frequency, of the light modulation, the machinery can appear to be stationary, or to move with another speed, potentially leading to hazardous situations. Stroboscopic effects that become visible in rotating objects are also referred to as the wagon-wheel effect. In general, undesired effects in the visual perception of a human observer induced by light intensity fluctuations are called Temporal Light Artefacts (TLAs). Further background and explanations on the different TLA phenomena including stroboscopic effect is given in a recorded webinar “Is it all just flicker?”. In some special applications, TLMs may also induce desired effects. For instance, a stroboscope is tool that produces short repetitive flashes of light that can be used for measurement of movement frequencies or for analysis or timing of moving objects. Also stroboscopic visual training (SVT) is a recent tool aimed at improving visual and perceptual performance of sporters by executing activities under conditions of modulated lighting or intermittent vision. Root causes Light emitted from lighting equipment such as luminaires and lamps may vary in strength as function of time, either intentionally or unintentionally. Intentional light variations are applied for warning, signalling (e.g. traffic-light signalling, flashing aviation light signals), entertainment (like stage lighting) with the purpose that flicker is perceived by people. Generally, the light output of lighting equipment may also have residual unintentional light level modulations due to the lighting equipment technology in connection with the type of electrical mains connection. For example, lighting equipment connected to a single-phase mains supply will typically have residual TLMs of twice the mains frequency, either at 100 or 120 Hz (depending on country). The magnitude, shape, periodicity and frequency of the TLMs will depend on many factors such as the type of light source, the electrical mains-supply frequency, the driver or ballast technology and type of light regulation technology applied (e.g. pulse-width modulation). If the modulation frequency is below the flicker fusion threshold and if the magnitude of the TLM exceeds a certain level, then such TLMs are perceived as flicker. Light modulations with modulation frequencies beyond the flicker fusion threshold are not directly perceived, but illusions in the form