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EMF Aware

Light Flicker Tool

Analyze a light source, TV, monitor, phone, tablet, e-reader or projector—or compare several devices side by side. The analysis changes automatically for lighting versus displays.

Compare up to 8 lights or displays

This is a screening and comparison tool. Lighting standards are not automatically valid for TVs, monitors, phones, tablets or other displays. Display results are therefore identified as screening guidance rather than certification. It does not replace formal laboratory testing, product certification, or medical advice.
Guidelines and interpretation notes

IEEE 1789-2015

Frequency-dependent modulation guidance for high-brightness LED lighting. This older recommended practice is specific to LED modulation and should not be directly applied to incandescent or halogen lamps. It does not fully characterize complex waveforms, multiple harmonics, phantom-array effects, or individual sensitivity.

California Title 24 JA8/JA10

The simplified screen uses less than 30% modulation below 200 Hz. Formal compliance requires raw waveform data, specified filtering, test conditions and required output levels. The optical waveform of incandescent or halogen lighting can be compared, but formal JA8 applicability depends on the product and installation category.

WELL Building Standard

For electric lighting in regularly occupied spaces, a commonly used WELL pathway is PstLM ≤ 1.0 and SVM ≤ 0.6. This pathway can be used for incandescent and halogen sources as well as LED lighting because it evaluates the measured optical waveform rather than the lamp technology. IEEE 1789 should not be used for incandescent or halogen lamps. Decorative, emergency and other excluded lighting categories may be treated differently, and the applicable WELL version and addenda should be confirmed for formal certification.

EU Ecodesign

For applicable mains-operated LED and OLED light sources at full load, the comparison values used here are PstLM ≤ 1.0 and SVM ≤ 0.4. These are regulatory product limits for applicable LED and OLED sources; for incandescent and halogen lamps they are shown only as an informational comparison.

Building Biology SBM-2024

A precautionary approach favouring uniform light, low harmonic content, and approximately 1% modulation or less, particularly below about 3,000 Hz. This is a highly conservative target and can be difficult to achieve with many modern LED lamps, drivers and dimming systems—especially at reduced light levels. Exceeding 1% does not automatically mean a light is unsafe; it means the source does not meet this particularly precautionary Building Biology objective and should be considered alongside frequency, waveform, SVM, PstLM and occupant sensitivity.

Metric limitations

Percent flicker and Flicker Index do not adequately account for frequency-dependent visual sensitivity. PstLM primarily addresses visible flicker, while SVM addresses stroboscopic visibility associated with motion.

TVs, phones, tablets and displays

IEEE 1789, California JA8/JA10, WELL and EU Ecodesign are lighting standards and should not be presented as formal display pass/fail standards. PstLM and SVM may be entered for informational context, but they are not treated here as validated display health or certification metrics. Display analysis must also consider refresh rate, PWM or modulation frequency, brightness setting, variable refresh rate, black-frame insertion, local dimming, screen content and eye movement.

ISO 9241-307 for electronic displays

ISO 9241-307 is the most directly relevant standards framework included here for electronic visual displays. It addresses display-oriented analysis and test methods, including temporal and spatial instability. This calculator does not perform the complete ISO procedure and cannot certify compliance; it provides a practical screening interpretation only.

Scientific literature: flicker, SVM and individual sensitivity

Why the subject is more complicated than one number

Temporal light modulation can produce directly visible flicker, stroboscopic effects during movement, phantom-array effects during rapid eye movements, visual discomfort, eyestrain, headache, altered task comfort and—among a small susceptible population—photosensitive seizures. SVM predicts the visibility of the stroboscopic effect under defined test conditions. It is not a complete measure of health risk, migraine sensitivity, direct flicker, phantom arrays or every individual response.

Two people can experience the same light differently because response is influenced by neurological susceptibility, migraine or visual-stress history, photosensitive epilepsy, age and visual physiology, eye movements, adaptation, fatigue, exposure duration, source brightness, field of view, waveform, duty cycle, spectrum, contrast, movement and dimming level.

Displays add further variables, including refresh rate, frame-rate control, pixel response, backlight dimming, OLED emission timing, local dimming, brightness setting, content, viewing distance and eye movement. A screen can therefore have a stable refresh rate but still use separate pulse-width modulation to control brightness.

Relatively well established

  • Low-frequency, high-contrast flashing can provoke seizures in susceptible people.
  • Temporal modulation can produce visible flicker, stroboscopic effects and phantom arrays.
  • Frequency, modulation depth, waveform, illumination and viewing conditions affect visibility.
  • Migraineurs and people with visual stress may respond differently from average observers.
  • Rapid eye movements can reveal temporal artefacts at frequencies well above traditional flicker-fusion thresholds.

Supported, but not fully quantified

  • Headache, eyestrain, fatigue or performance effects may occur without obvious conscious flicker.
  • Longer exposure, dimming, waveform shape, spectrum and harmonic content may affect comfort.
  • Some individuals may react at levels tolerated by most study participants.

Not established by current evidence

  • A universal frequency above which flicker is harmless for everyone.
  • A single percent-flicker, SVM or PstLM value that guarantees no health effects.
  • That SVM below 1.0 means a light is health-neutral.
  • That compliance with a lighting guideline guarantees comfort for sensitive occupants.
Practical interpretation: A passing result means the entered measurement meets that guideline’s comparison value. It does not mean the light is flicker-free or guaranteed to be comfortable for every occupant. For a person with migraine, visual stress, known light sensitivity or photosensitive epilepsy, use the lowest-modulation option reasonably available and assess the complete installed system in the actual room.

Reviews and broader scientific context

  1. A flashing light may not be that flashy: a systematic review on critical flicker fusion frequencies.
  2. Neuropsychological and neurophysiological mechanisms behind flickering light stimulus processing.
  3. Visual discomfort and flicker.

SVM and stroboscopic effects

  1. Perz et al. — Modeling the visibility of the stroboscopic effect occurring in temporally modulated light systems.
  2. Perz — Setting the stroboscopic visibility threshold.
  3. Veitch and Martinsons — Detection of the stroboscopic effect by young adults varying in sensitivity.
  4. Sekulovski et al. — Effects of long-term exposure to stroboscopic effect from moderate-level modulated light.

High-frequency artefacts and eye movement

  1. Davis et al. — Humans perceive flicker artifacts at 500 Hz.
  2. Roberts and Wilkins — Flicker can be perceived during saccades at frequencies in excess of 1 kHz.

Migraine, visual discomfort and sensitivity

  1. Detection and discrimination of flicker contrast in migraine.
  2. Photophobia in migraine: an interictal PET study of cortical hyperexcitability.
  3. Cortical hyperexcitability in migraine and aversion to patterns.
  4. Visual discomfort and flicker.

Photosensitive epilepsy

  1. Photosensitivity and epilepsy: current concepts and perspectives.
  2. Two visual mechanisms of photosensitivity.
  3. Treatment of photosensitive epilepsy using coloured glasses.

Workplace comfort and performance

  1. Küller and Laike — Impact of flicker from fluorescent lighting on well-being, performance and physiological arousal.
  2. Wilkins — Intermittent illumination affects movements of the eyes across text.

This reading list is educational and is not a systematic review, medical diagnosis or substitute for clinical guidance. Study methods and exposures vary, and findings from fluorescent lamps, displays and laboratory stimuli do not always transfer directly to every modern LED installation.

EMF Aware · Health-informed electrical and technology designFlicker screening tool v2.1.0

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