Temporal variation in the light output of light sources and lighting systems (temporal light modulation, TLM) is sometimes a feature (e.g. signal flashes) but more often is an undesirable side-effect of product or system design and/or operation. TLM explains the association of magnetically-ballasted fluorescent lighting systems with headache and eyestrain complaints. These complaints largely disappeared following the adoption of electronic ballasts, but the introduction of light-emitting diode (LED) lamps and lighting systems has renewed researcher, manufacturer, and regulator attention to TLM.
This presentation will provide a brief overview of some of the visual, behavioural, and neurological problems that TLM can cause, identifying some of the most urgent research questions and describing why TLM is a very difficult lighting parameter to measure and to investigate.