Also flicker on bad LED lighting. A lot of bad LED lighting flickers at ~60Hz. In rooms lit by that, you can wave your hand or a thin object back and forth, and if you look carefully, you can perceive a "shutter" effect where you're only seeing the snapshots of its position where the light is on.
The thing that makes that so insidious is that not everybody can easily perceive that.
(The reason why such flicker is common in cheap LED bulbs: they turn AC into DC using a half-wave rectifier, which just chops off half the AC wave. This is also why you can still see the effect in rooms lit by multiple lights, because the flicker is in sync, synchronized to the incoming AC.)
If you are building a space for other people and you are responsible for the lighting, please check for this. If you can't perceive it yourself, find someone who can.
> In rooms lit by that, you can wave your hand or a thin object back and forth, and if you look carefully, you can perceive a "shutter" effect where you're only seeing the snapshots of its position where the light is on.
Heh, this is how I test these lamps as well. Also my camera has anti-flicker shutter which can detect it to thwart it by syncing the shutter release with flicker itself. It shows a warning when it detects is, as well.
> Also my camera has anti-flicker shutter which can detect it to thwart it by syncing the shutter release with flicker itself. It shows a warning when it detects is, as well.
Nice! Which cameras do this? And I wonder, how cheaply could a sensor be made to do this, that shows on the screen "there's flicker at 60Hz / 120Hz / 480Hz", if it didn't also need to be a great camera (e.g. it only captured at 480p)?
Mine is a Sony A7-III, the setting is called Anti-flicker shoot. I believe many modern mirrorless systems have the capability.
However, I wouldn't say "oh that's easy", because A7-III has two realtime DSPs, and one of them is directly responsible for things like real-time focusing, face/object/eye recognition and real time tracking, etc. So, I believe that DSP is handling the flicker detection as well.
...and A7-III is the "entry level" member of its generation. higher end models have more computing power than that.
[−]dreamcompiler · 2026-11-15 Sun 17:28 UTC ·
link
The power supply is the weak point in LED room lighting. The best power supply for LEDs is switch-mode PWM, high frequency, and with thermal management designed by an engineer who understands therodynamics.
Unfortunately all those things are expensive so you rarely find such bulbs in the cheap bin at Home Depot.
Bulbs are actually a very bad form factor for LEDs, because they concentrate two heat-generating components - the PSU and LEDs - into a small chassis. LED tape with a separate power supply is probably the best solution that's not a full-custom DC light fixture.
> If you can't perceive it yourself, find someone who can.
Or just use your phone’s slo-mo feature to take a 240 FPS video (which then gets played back at 30 FPS). 60 Hz flicker becomes extremely visible. More than once I’ve noticed the strobe effect and then confirmed it this way.
The thing that makes that so insidious is that not everybody can easily perceive that.
(The reason why such flicker is common in cheap LED bulbs: they turn AC into DC using a half-wave rectifier, which just chops off half the AC wave. This is also why you can still see the effect in rooms lit by multiple lights, because the flicker is in sync, synchronized to the incoming AC.)
If you are building a space for other people and you are responsible for the lighting, please check for this. If you can't perceive it yourself, find someone who can.
Heh, this is how I test these lamps as well. Also my camera has anti-flicker shutter which can detect it to thwart it by syncing the shutter release with flicker itself. It shows a warning when it detects is, as well.
Nice! Which cameras do this? And I wonder, how cheaply could a sensor be made to do this, that shows on the screen "there's flicker at 60Hz / 120Hz / 480Hz", if it didn't also need to be a great camera (e.g. it only captured at 480p)?
However, I wouldn't say "oh that's easy", because A7-III has two realtime DSPs, and one of them is directly responsible for things like real-time focusing, face/object/eye recognition and real time tracking, etc. So, I believe that DSP is handling the flicker detection as well.
...and A7-III is the "entry level" member of its generation. higher end models have more computing power than that.
Unfortunately all those things are expensive so you rarely find such bulbs in the cheap bin at Home Depot.
Or just use your phone’s slo-mo feature to take a 240 FPS video (which then gets played back at 30 FPS). 60 Hz flicker becomes extremely visible. More than once I’ve noticed the strobe effect and then confirmed it this way.