The tests have proved that maximum arduousness occurs at the frequency of about 9 changes per second. The most sensitive light sources are traditional incandescent bulbs with tungsten filament. Halogen bulbs, which filaments have much higher temperature, have also much higher inertia which reduces the perceived brightness changes. Fluorescent lamps have the best flicker “resistance”, as due to their some specific properties they stabilize the current flowing through the lamp during the voltage changes, and thus reduce the fluctuations.
What light sources can be effected by flicker?