PWM flicker: Invisible light that's harming our health?

Original Article ↗ Hacker News Discussion ↗

Personal Sensitivity and Everyday Impact

  • Multiple commenters report PWM and low‑frequency LED flicker triggering migraines, eye pain, or strain; some can’t tolerate common smart bulbs or OLED phones.
  • Others don’t get headaches but find LED lighting and car headlights uncomfortably bright, harsh, or ruining nighttime ambience in neighborhoods.
  • A few note they coped in offices or stores by adding incandescents or working near windows; some now actively avoid certain devices and fixtures.

Technical Discussion: How and Why LEDs Flicker

  • Many bulbs use simple rectified mains (100/120 Hz) or low‑frequency PWM for dimming; cheap designs skip proper filtering, leading to visible flicker or stroboscopic effects.
  • More sophisticated approaches:
    • High‑frequency PWM (kHz range) plus inductors/capacitors to smooth current.
    • Constant‑current switching supplies (“DC dimming”) that avoid PWM at the LED, though they’re costlier.
  • Modulation depth (how “fully off” the dark phase is) matters as much as frequency; deep on/off cycles are more disturbing than shallower modulation.
  • Legacy TRIAC wall dimmers can cause severe flicker with LEDs designed for chopped AC rather than DC drivers.

Devices and Screens

  • Many phones, OLED displays, and some laptops use PWM for brightness control; several commenters say modern Apple devices in particular cause eye pain, while some older LCD or specific Android models do not.
  • Tools like slow‑motion video, high‑shutter camera apps, notebook review sites, and dedicated flicker meters are used to detect PWM.

Quality of Light: Color, CRI, and “Feel”

  • Beyond flicker, people complain that many LEDs render reds and skin tones poorly and feel “off” despite high CRI scores.
  • Discussion touches on CRI, extended R9 red rendering, newer metrics (TM‑30), and tint (greenish vs pinkish). Premium bulbs (high CRI, “Eye Comfort” lines, some specialty brands) are praised.

Health Risks, Evidence, and Standards

  • Some see PWM sensitivity as clearly real and debilitating; others think broader “health risk” claims resemble Wi‑Fi/MSG scare writing.
  • IEEE 1789 is cited as recognizing flicker‑related risks and defining low‑risk regions by frequency and modulation, but commenters argue the article overinterprets it and invents its own “risk levels” without solid citations.
  • There’s agreement that discomfort, distraction, and headaches are real for some people; long‑term or population‑level harms remain unclear.

Workarounds and Buying Advice

  • Strategies: choose non‑dimmable or high‑quality dimmable bulbs, warm color temperatures, high‑CRI products, or videography/”flicker‑free” panels.
  • Resources mentioned: independent bulb test sites for flicker and CRI, and using hand‑waving or phone slow‑mo as crude flicker tests.
  • Some are stockpiling incandescents or using halogens despite efficiency penalties; others argue LED lifetime and energy savings dominate environmental and cost concerns.