# CSTB Position Statement: The adverse Effects of Temporal Light Modulation of Lamps and Luminaires: Impacts on Health, Safety and Visual Comfort

Christophe Martinsons

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Christophe Martinsons. CSTB Position Statement: The adverse Effects of Temporal Light Modulation of Lamps and Luminaires: Impacts on Health, Safety and Visual Comfort. 2018. hal-05321748

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CSTB

le futur en construction

The adverse effects of
temporal light modulation
of lamps and luminaires:
impacts on health, safety
and visual comfort

<figure><img src="image_2.png" /></figure>

Christophe Marlinsons
2018.04.20 09:49:49 +0200
CSTB
le futur en construction

# The adverse effects of temporal light modulation of lamps and luminaires: impacts on health, safety and visual comfort

Dr. Christophe Martinsons

20/04/2018
# Definition of temporal light modulation of LED products

Temporal light modulation refers to rapid fluctuations of light, periodic or not [CIE 2016]. In the case of solid-state lighting products, this phenomenon is linked to the ultra-fast response of LEDs to the variations of electrical current. Undesired temporal light modulation can also be caused by the association of an LED lighting product with a non-compatible lighting control device.

In most cases, the temporal light modulation of a lighting system can be characterized by a dominant frequency modulation and a modulation amplitude expressed in percentage.

According to the modulation frequency and the value of the modulation amplitude, different effects may appear in humans:

* **Visual effects:** flicker, stroboscopic effect, phantom array effect

* **Non-visual effects:** modification of ocular movements, decrease of visual performance

* **Health effects:** accidents caused by visual effects, epileptic seizures, eye strain, visual fatigue, headaches and migraines.

Flicker is the visual perception of the temporal light modulation in the specific case of a fixed observer and a stationary light source [IEC 2017]. This effect is directly observable up to modulation frequencies of about 70 Hz. **Flicker is not visible** when the modulation frequency is 100 Hz, as is the case with most lighting products.

Stroboscopic effect is a visible decomposition of the motion of a moving object when this object is lit up by a temporally modulated light [IEC 2018]. When the moving object is a body part, this effect is typically visible when the modulation frequency is between 70 Hz and 2 000 Hz [NEMA 2015].

The phantom-array effect is the perception of a series of multiple images of a temporally modulated light source during an ocular saccade. This effect can be observed at frequencies up to 2 500 Hz.

Table 1 presents the known effects of temporal light modulation. The colored vertical bar indicates effects appearing at 100 Hz. The vast majority of lighting products sold in the EU have a temporal light modulation at 100 Hz.

<table><caption>Table 1. Overview of the effects of temporal light as a function of the modulation frequency. The red bar indicates the frequency of 100 Hz, the most commonly found in European lighting products.</caption><thead><tr><th>Frequency (Hz)</th><th>1 Hz</th><th>20 Hz</th><th>70 Hz</th><th>100 Hz</th><th>1000 Hz</th><th>2000 Hz</th><th>3000 Hz</th></tr></thead><tbody><tr><th>Effects</th><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><th>Visual effect</th><td></td><td></td><td><u>Flicker</u><br>Standard IEC/TR 61547-1:2017</td><td></td><td><u>Stroboscopic effect</u><br>standard IEC/TR 63158:2018<br><u>Phantom array effect</u><br>Technical note CIE TN 006:2016</td><td></td><td></td></tr><tr><th>Non-visual effect</th><td></td><td></td><td></td><td><u>Modification of ocular movements</u><br>Standard IEEE 1789:2015<br><u>Decrease of visual performance</u><br>Standard IEEE 1789:2015</td><td></td><td></td><td></td></tr><tr><th>Health effects</th><td></td><td></td><td></td><td><u>Trigger of epileptic seizures</u><br>Standard IEEE 1789:2015<br><u>Eye strain, visual fatigue</u><br><u>Headaches</u><br>Standard IEEE 1789:2015<br><u>Migraines and paroxysmal headaches</u><br>Standard IEEE 1789:2015</td><td></td><td></td><td></td></tr></tbody></table>
## EU regulatory context

The current EU regulations for lamps and luminaires (eco-design of energy-related products) do not include any limits on temporal light modulation.

## Normative context

Prior to 2015, hardly any standards describing temporal light modulation and its effects existed. Since 2015, new standards and technical documents have been published by most standardization bodies such as CIE, IEEE, NEMA and IEC.

In these recent documents, flicker is the best described effect. Several indices were introduced to quantify flicker perception, most notably P<sub>st</sub><sup>LM</sup>, the short-term flicker severity index, which has already been in use for many years in EMC testing (electromagnetic compatibility). Several standardization bodies also introduced the SVM index, which relates to the visibility of the stroboscopic effect during hand motion.

Current lighting product safety and performance standards do not include any limits of temporal light modulation. Furthermore, standards concerning control gears do not ensure a perfect compatibility with LED lamps and luminaires, which may lead to anomalous temporal light modulation.

The only standard which gives recommendations aimed at protecting human health is the North American standard IEEE 1789. The IEEE 1789 recommendations rely on a health expertise based on a risk analysis.

A specific requirement of the IEEE 1789 standard is to limit the modulation percent to 8% at the frequency of 100 Hz, to ensure a low-risk level. This limit was exceeded with the old lighting technologies (fluorescent lamps with magnetic ballast). This limit is currently exceeded by many modern LED lamps currently sold in the EU.

## Actions to limit health impacts and visual discomfort resulting from temporal light modulation

The following actions should be undertaken to avoid or minimize the adverse effects of temporal light modulation of lamps and luminaires:

- Define regulatory limits in the next EU eco-design regulation to protect the population against adverse visual, non-visual and health effects; and not only flicker.

- Define a limit on temporal light modulation at 100 Hz, occurring for the vast majority of LED lamps and luminaires available on the European market.

- Define a limit for the modulation amplitude at 100 Hz consistent with the recommendations of the IEEE 1789 standard: low-risk limit of 8% at 100 Hz. Laboratory measurements showed that 57% of LED lamps sold in the EU already comply with this recommendation.

## Relevant standards and technical documents

<table><tr><td>CIE 2016</td><td>CIE TN 006:2016, Visual Aspects of Time-Modulated Lighting Systems – Definitions and Measurement Models</td></tr><tr><td>IEEE 2015</td><td>IEEE 1789:2015, IEEE Recommended Practices for Modulating Current in High-Brightness LEDs for Mitigating Health Risks to Viewers</td></tr></table>
<table><tr><td>IEC 2017</td><td>IEC TR 61547-1: 2017, Equipment for general lighting purposes - EMC immunity requirements- Part 1: An objective light flickermeter and voltage fluctuation immunity test method</td></tr><tr><td>IEC 2018</td><td>IEC TR 63158: 2018, Equipment for general lighting purposes – Objective test method for stroboscopic effects of lighting equipment</td></tr><tr><td>NEMA 2017</td><td>NEMA 77:2017 Temporal Light Artifacts: Test Methods and Guidance for Acceptance Criteria</td></tr></table>
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