Flicker (PstLM index) is a short-term, unintended fluctuation in light intensity. It may be visible to the naked eye or completely hidden, yet still cause discomfort and health symptoms. The stroboscopic effect (SVM – Stroboscopic Visibility Measure) is a disturbance in motion perception. Under fluctuating light, a rotating element may appear stationary or seem to move in the opposite direction, which in an industrial environment poses a real hazard.
The two phenomena differ in mechanism and impact. Flicker is mainly related to power quality and LED drivers, while the stroboscopic effect results from rhythmic flashes of light that disrupt the way the brain interprets motion.
How do flicker and stroboscopic effect affect humans?
Flicker usually starts innocently. In a conference room, office, or classroom, the light subtly changes its intensity. At first, no one notices, but after an hour headaches, eye strain, and concentration problems appear. Studies indicate that prolonged exposure to unstable light contributes to migraines and worsens well-being.
The stroboscopic effect works differently. It does not primarily affect visual comfort, but motion perception. In production halls or workshops, a technician may incorrectly assess the speed of a rotating shaft or rotor. This leads to mistakes and increases the risk of accidents. For people with photosensitive epilepsy, rhythmic flashes at certain frequencies pose an additional danger, as they can trigger seizures.
Causes of unstable light
There is no single source of the problem. The most common causes are:
- unstable voltage in the power grid, disrupting steady current flow,
- low-quality LED drivers that fail to filter current fluctuations and cause pulsations,
- unsuitable dimmers incompatible with the given light source type,
- poor-quality electronic components, aging capacitors, and circuits.
In traditional incandescent bulbs, the filament acted as a natural buffer and softened power fluctuations. LEDs react instantly, so proper driver electronics are crucial for lighting quality.
Ecodesign standards and EU requirements
Since September 2021, Commission Regulation (EU) 2019/2020 has been in force, regulating both energy efficiency and light quality. The document sets specific limits:
- PstLM ≤ 1.0 – flicker limitation,
- SVM ≤ 0.4 – stroboscopic effect limitation at full load of the source.
Although some sources (e.g., certain industrial lamps or HID lamps) are exempt, most products on the market must comply. This ensures that consumers receive equipment that not only saves energy but also guarantees user safety.
Conscious use of the stroboscopic effect
The stroboscopic effect is not always undesirable. In entertainment, it is deliberately used to build the atmosphere of concerts and shows. Photography and film use it to capture motion in ways impossible under natural light. In industry, it serves to observe fast technological processes, while in emergency vehicles it acts as an intense warning signal.
However, in all these applications it must be used carefully and with safety in mind. Strobe light that draws attention at a concert could create a serious risk for machine operators in a production hall.
How to reduce the risk of flicker and stroboscopic effect?
The most effective measures combine good design with quality components.
In practice, this means:
- using high-class LED drivers that ensure stable power supply,
- choosing certified light sources labeled as Flicker Free, Flicker Free,
- matching dimmers to specific types of luminaires,
- auditing and regularly maintaining installations,
- using voltage regulators in places particularly exposed to power fluctuations.
This approach not only eliminates health issues and improves user comfort but also ensures compliance with EU regulations.
The role of RCC in light stability testing
The RCC Research and Development Center specializes in measuring both flicker (PstLM) and stroboscopic effect (SVM). Tests are carried out according to IEC TR 61547-1 using laboratory photometers and advanced equipment for recording light waveforms.
The process includes not only recording and analysis but also detailed interpretation of results by engineers with many years of experience. This provides manufacturers and distributors with reports that form the basis for placing products on the European market and confirming their quality.
Products that pass RCC tests successfully may be labeled with the RCC Flicker Free mark. For customers, this is a clear signal that the luminaire is safe, compliant with ecodesign requirements, and tested by an independent laboratory.
Stable light as the foundation of modern lighting
Today’s lighting systems must be both energy-efficient and healthy for users. Flicker and stroboscopic effect are not minor inconveniences but real factors influencing well-being, productivity, and safety.
Research conducted at RCC helps eliminate products that do not meet standards from the market, thereby shaping a new quality benchmark. Stable light means greater comfort at work and study, better well-being, and a higher level of safety – both at home and in industrial environments.