Temporal modulation of light, usually at twice the mains frequency (100 or 120 Hz) from drivers with poor ripple filtering, or at the switching frequency of PWM dimming. It is described by percent flicker, flicker index and metrics such as Pst LM for visible flicker and SVM for stroboscopic effects. Even invisible flicker is linked to headaches and eye strain in sensitive people, and it creates banding on camera.
Camera shows banding under the corridor lights at low dim, the driver's PWM is flickering at around 400 Hz.
Also heard as
- temporal light modulation
- TLM
Related terms
Stroboscopic effect
The way moving or rotating objects look stopped, slowed or multiplied under light that flickers.
Driver
The electronic power supply that converts line voltage into the regulated current or voltage an LED needs.
Dimming curve
The relationship between a dimmer or control signal and the light output it produces.
LED
Light-Emitting Diode: a semiconductor light source, made white for lighting by coating a blue chip with phosphor.