I have a floor lamp (standing lamp which spreads light via the ceiling). It uses LEDs and it's dimmable. When I capture the light with a camera I can clearly see oscillations.

It is known that PWM-dimmed monitors can cause eye strain: https://www.flatpanelshd.com/focus.php?subaction=showfull&id=1362457985.

My question is: can a floor lamp which emits PMW-dimmed light also cause eye strain?


closed as off-topic by Scott Seidman, winny, ThreePhaseEel, Wesley Lee, PeterJ Dec 13 '17 at 1:04

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    \$\begingroup\$ I'm voting to close this question as off-topic because this is physiology, not engineering \$\endgroup\$ – Scott Seidman Dec 12 '17 at 22:36
  • \$\begingroup\$ It sure can. A simple google search will give you plenty of results to go on. \$\endgroup\$ – winny Dec 12 '17 at 22:37
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    \$\begingroup\$ It brings awareness to PWM light designers to use >500Hz \$\endgroup\$ – Sunnyskyguy EE75 Dec 12 '17 at 22:53

If the frequency is low and the lumen intensity is 250 lumen/m² which is typical for TV's and monitors then yes. But prudent designers use a PWM rate higher than the eye can respond which is about 10ms for staring and 1ms for eye or target light motion with peripheral vision. (Cadillac made the mistake on 1st invention of PWM brake lights using 500Hz which is undetectable when staring at, but moving car and or roving eye can detect the flicker, but not really a eye strain, just a threshold of eye response.)

However your camera shutter rate is faster than the eye, so it may not be proof of a frequency and intensity product that causes eye strain.

Basically excessive lumen/m² direct into the eye causes the greatest eye strain when the background is relatively dim. Which is why many bar TV's have perimeter LEDs to allow the eye iris to constrict light coming in. The glare of the perimeter backlights actually helps the eye adjust to the brightness of the big screen TV's.

This is why I always adjust my screen brightness to the minimum tolerable level to avoid eyestrain when using for extended hours of viewing. That works for me.

  • \$\begingroup\$ "Cadillac made the mistake on 1st invention of PWM brake lights using 500Hz which is undetectable when staring at, but moving car and or roving eye can detect the flicker" - As someone who's fairly sensitive to this, I can attest it's not just Cadillac and not just brake lights. \$\endgroup\$ – marcelm Dec 12 '17 at 23:05
  • \$\begingroup\$ yes but they were the first car makers to make this misteak (lol) which is why this question is of great importance to EE PWM luminaire designers. Some people have a greater sensitivity to peripheral and motion flicker. \$\endgroup\$ – Sunnyskyguy EE75 Dec 12 '17 at 23:29
  • \$\begingroup\$ Underlying LED (blue?) could certainly output pulses of PWM'd current. But what about phosphors used in white LEDs? I've seen phosphor time constants in the 10ms ballpark. This gets complicated, where short wavelengths get modulated more than long wavelengths. \$\endgroup\$ – glen_geek Dec 12 '17 at 23:44
  • \$\begingroup\$ Yttrium Aluminum Garnet (YAG:Ce) phosphor (doped with cerium) on LEDs have a very fast decay time, even on "remote phosphor" bulbs. Even with added nitrides and oxynitrides doped with Europium(Eu) to improve CRI esp. on cool whites, still have a fast decay time to prevent saturation quenching. @glen_geek ? Where have you seen 10ms? UV CRT's? \$\endgroup\$ – Sunnyskyguy EE75 Dec 13 '17 at 0:59

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