The Flicker Tester app for iPhone from Viso Systems for the first time makes it possible to measure flickering coming from LED light sources and LED video screens. The app will give you directly flicker index, flicker percentage and flicker frequency values including the full flicker curve.
Ensure accurate flicker measurement by diffusing the image entering the camera.
Until recently lighting engineers paid little attention to the effects of imperceptible flicker. However, toughening of health and safety rules, better research, and increasing complaints from staff working in offices illuminated by ubiquitous fluorescent tubes have led to calls for action.
But without a definition of flicker, who’s to say whether one light source is better than another? The Illuminating Engineering Society of North America (IESNA) has addressed this challenge and come up with a definition of “percent flicker” and “flicker index” in the ninth edition of The IESNA Lighting Handbook. Figure 1 shows how the metrics are defined.
Flicker percent is a relative measure of the cyclic variation in the output of a light source (i.e. percent modulation). This is also sometimes referred to as the “modulation index.”
From the figure: Percent flicker = 100 x (A – B)/(A + B)
Flicker index is a “reliable relative measure of the cyclic variation in the output of various sources at a given power frequency. It takes into account the waveform of the light output as well as its amplitude,” according to the handbook. The flicker index assumes values from 0 to 1.0, with 0 for steady light output. Higher values indicate an increased possibility of noticeable lamp flicker, as well as stroboscopic effect.