Flickerfrekvens

Flickerfrekvens, or flicker frequency, is the rate at which the brightness of a light source changes over time, typically measured in hertz (cycles per second). It reflects how often the light completes a full increase-and-decrease cycle within one second and is influenced by the electrical drive or control method used for the source.

Common causes include alternating current (AC) mains power, which in many regions operates at 50 Hz (or 60 Hz) and can produce flicker at 50/60 Hz or at its harmonics. When lighting is rectified or when LED drivers use pulse-width modulation (PWM) for dimming, flicker can occur at higher frequencies such as 100/120 Hz or at the PWM frequency. The thermal inertia of incandescent lamps can smooth rapid fluctuations, while fluorescent and some LED sources are more prone to visible flicker.

Perception of flicker varies widely. Most people do not notice flicker above roughly 60 Hz, but sensitive individuals may perceive it at higher frequencies, or during certain light levels and motion. Prolonged exposure to perceptible flicker can cause eye strain, headaches, or, in rare cases, trigger photosensitive seizures. This motivates limits and measurement methods in lighting standards.

Measurement is carried out with specialized equipment that analyzes brightness fluctuations over time. Metrics such as flicker percentage, flicker index, and flicker severity (FS) are used to assess potential impact. Standards from IEC, ISO, and regional regulatory bodies define acceptable flicker levels for lighting products.

In display technology, higher refresh rates and constant pitch between frames reduce perceived flicker, while in photography and videography, flicker can interact with exposure and rolling shutters, causing banding unless lighting frequencies and camera settings are matched.