I have LED in my home office. The "temperature" and this flicker were driving me bonkers. Fortunately no headache. Now I have them all pointed away to reflect off wall or ceiling, or behind diffusers. Much less bothersome,
mtalantikite · 3h ago
These LED light flickers actually trigger ocular migraines for me. I had tried to put in LEDs when the incandescent ban hit the US, and ended up with a Philips Hue system. I had 4 migraines in 3 days and had to send them back. I purchased as many incandescent bulbs as I could find, but they were somewhat impossible to find at that point.
I've got a couple bulbs from Waveform Lighting and they don't flicker, but I totally can tell the reds are off.
I really hate the LED transition. My building replaced all the outdoor lights with them, and now it's just too bright to sit on my stoop at night like used to be so common here in Brooklyn. My backyard neighbor put in an LED floodlight and now I have to buy blackout curtains. I drive rarely, but the oncoming headlights are blinding when I do. It's pretty depressing if I think about it too much.
igor47 · 3h ago
That sucks; I feel your pain. I, too, strongly dislike overly bright lighting.
I wonder if there's room to at least engage with the neighbor to talk about friendlier light options? You might also be able engage with these folks to see if there are efforts to improve the lighting in new York: https://darksky.org/
PaulHoule · 3h ago
My take is that PWM dimmers are dramatically more energy efficient than the old rheostat dimmers people used to use. If you operate a transistor in a digital mode where it is either on or off it is close to 100% efficient, but if you operate it in a 50% power mode you have to send 50% of the power to a load and the other 50% to a resistor. Thus CMOS logic eradicated bipolar, switching power supplies replaced linear power supplies, a Class D amplifier can be a fraction the size of a Class A amplifier, etc.
You could probably still reduce the flicker by either increasing the switching frequency or putting some kind of filter network between the switch and the load.
mtalantikite · 3h ago
For sure, they're definitely way more efficient. They just unfortunately give me migraines. I'd be open to trying some that have a filter network or some other smoothing on the flicker.
But I've also never lived in a house that has dimmers (they've all been old homes in the north eastern US) and I never use overhead lighting, so it's not something I need or would miss.
card_zero · 2h ago
Apparently fourth-generation LED tube lights are designed not to flicker.
I wonder to the degree their effects are much worse than migraines. Perhaps irritability? Mental confusion? Anxiety? I'm spitballing here, but to be sure it seems like our world is somehow a place of more anxiety, irritation .... I would love for it to be something we could take control of.
genewitch · 3h ago
i doubt it's the light bulbs. I posited the other day, by assembling a few different ideas, that Trauma Based Entertainment is to blame for this. something like 2/3rds of all Television programing is law-enforcement adjacent. True Crime is super popular on TV, law and order, NCIS, FBI this-and-that. And what's one of the largest advertising cohorts?
Medicine for depression, anxiety, insomnia...
it's nearly a closed loop; something i intuitively realized shortly after 2001/09/11 - by the end of that year i decided i would no longer have a "Television" attached to CATV/SAT/ANT service.
I'm not sure if i am correct, i haven't really dedicated a lot of time to getting the exact numbers, talking to psychologists and sociologists and the like. But two people i know had "breakdowns" (grippy sock) in the last month and both of them always have true crime on TV in the background or listen to true crime podcasts. Shortly after that happened i was listening to the moe facts podcast where Moe used the term "trauma based entertainment" and something clicked - Moe didn't mention "it's because of pharma ads" - that's my own input after having worked for the largest television "broadcast" company in the world, just long enough to see the advertiser "dinner".
RiverCrochet · 54s ago
The only ones watching traditional OTA TV anymore are elders. That advertising cohort is why OTA TV ads are filled with pharmaceuticals and "you may be entitled to financial compensation" type ads, at least where I'm at. Traditional TV has been dying since Youtube and broadband.
> it's nearly a closed loop; something i intuitively realized shortly after 2001/09/11 - by the end of that year i decided i would no longer have a "Television" attached to CATV/SAT/ANT service.
Curiously this is about the same time I decided to give up on TV and radio as well.
SLHamlet · 1h ago
I had no idea about this:
"To understand why PWM bulbs have so much flicker, imagine them being controlled by a robot arm flicking the on/off switch thousands of times per second. When you want bright light, the robot varies the time so the switch is in the 'on' mode most of the time, and 'off' only briefly. Whereas when you want to dim the light, the robot arm puts the switch in 'off' most of the time and 'on' only briefly."
loph · 3h ago
I can tell you that lights strobing exacerbate my migraines. Even 120 hertz from fluorescent lights will affect me. I have mitigated this in the past by adding incandescent lights in my office, or demanding to work near a window. LED lamps are no good, as another commenter posted, even the simplest ones strobe. Incandescent bulbs grow harder to find as time goes on. Progress?
JKCalhoun · 3h ago
Suspicious of "DC dimming". If you can just lower the current to an LED to dim it, everyone would. Someone will know better than me, but I believe there is a kind of threshold voltage for the (solid-state) LED.
I am not aware of LED bulbs (and here I am talking about home lighting, not phones or laptops) that dim by shutting down some of the (multiple) LEDs.
Most home lighting bulbs appear to have several LED elements. A circuit could enable dimming by simply shutting some of them off — running the rest full-on. 50% dim would of course shut half the LEDs off. No PWM required.
Kirby64 · 3h ago
DC dimming LEDs is relatively easy, and somewhat common. The problem is that it's expensive compared to PWM dimming. It requires more expensive current-adjustable circuitry.
Additionally, for bulbs that are used in regular household fixtures, they basically need a way to convert TRIAC chopped 50/60Hz AC into constant current... which makes things even more expensive. Smart bulbs that are supplied a constant non-chopped AC can do it easier, but it's still expensive to do DC dimming.
PaulHoule · 2h ago
I guess there is some threshold below which the LED turns off so the voltage/current -> light function needs to be set accordingly.
When I was in high school we were messing around with liquid nitrogen and overvolting LEDs and noticed the odd effect that the color of the LED would change if you overvolt it. It was years before I found out why
Voltage, yes. Current, no not really. You can drive extremely low currents and still get photon emissions from LEDs. That said, it's highly non-linear, so you basically need to assign set points. Doubling the current won't double the lumen output.
mrob · 3h ago
You can just lower the current. Not everyone does because it generally requires more expensive components, e.g. inductors. There is a threshold voltage ("forward voltage") needed for LEDs to turn on but there's no threshold for minimum radiant flux. LEDs are actually more efficient at low current (although this might be counteracted by greater losses in the power supply).
kjkjadksj · 3h ago
You can in fact dim leds. You can see a lot of controllers that are just that at various parts suppliers.
genewitch · 3h ago
you can dim LED that are running on DC (it requires more than a potentiometer i guess - probably a buck circuit controlled by a pot, though) or AC; i have scant idea how the AC ones work, although variacs have existed for a real long time; but you have to buy special LED bulbs that can handle being on a dimming circuit.
this is different than a bulb like hue etc that have the ability to dim themselves through whatever mechanism.
SAI_Peregrinus · 22m ago
Traditional dimmers used TRIACs. Those don't dim LEDs well, they make very visible flicker. TRIACs turn the AC off for part of the waveform, essentially a very slow version of PWM. With an incandescent filament that flicker isn't as noticeable since it takes some time to cool down & stop glowing, which visibly smooths the flicker. It just stabilizies around a lower temperature. With LEDs, the turn-off is nearly instant. You visibly see the flicker at the AC mains frequency.
There are two ways to dim an LED: supply less current at the same voltage, or PWM dim it with a fast enough switching speed that you don't notice the flicker (this being slower than it needs to be is what the article is about). A current source is pretty easy to build, and doesn't flicker, but it does dissipate all the excess energy as heat. That's not what you want inside the dimmer switch in your wall, it can be quite a lot of heat and would be a fire hazard in such a confined area. It does work for things like photography lamps which can have exterior heat sinking.
blacksmith_tb · 3h ago
I would certainly agree that finding LED bulbs that you like and/or don't bother you can take some work (especially if you want to put them on a dimmer, in which case you may also need to replace your dimmer). However, I am skeptical that subtle PWM flickering is unavoidable. For the chateau example, it would be better to choose bulbs with fewer lumens and run them at 100%?
baggachipz · 3h ago
I wonder about this too. If I have a dimmer and a LED bulb, does putting the dimmer all the way up still use PWM? I have a hunch that it still does, but would love to be proven wrong.
orwin · 2h ago
I flagged because this is a submarine ad, but it was still interesting tbh.
satiated_grue · 2h ago
"Perceiveved brightness"?
And perceiveved brightness is equal to the peak of the PWM wave?
That image from courtesy Daylight Computer Company is consuming too much of my attention.
Jazgot · 3h ago
There is a strong and widespread tendency to view anything artificial as highly dangerous. I understand this perspective, but on the other hand, we have science and reasoned arguments.
normie3000 · 3h ago
Do computer screens flicker and release this bad light?
For OLED I remember reading that PWM dimming is necessary because DC dimming causes shifts in color/whitepoint.
codethief · 3h ago
Some do, some don't. Sites like notebookcheck.net typically mention in their reviews whether a given laptop screen exhibits PWM.
igor47 · 3h ago
In the article they rank some smartphones by how much they flicker for dimming, I assume it's the same when computer screens dim?
swayvil · 48m ago
We had these flourescents in our computer lab at school. They were light yet dark. On yet off. Crazy. Some weird color or flickering frequency. If you sat there for a couple of hours you would start to stink. Like, a weird stink. Some speculated that it did something to your glands.
Give me a nice candle.
swayvil · 24m ago
Hey it got flagged.
Why do we use anonymity for that? What's gained and lost by that?
demosthanos · 3h ago
I know that people anecdotally report complaints about flicker and it's plausible to me that there could be an effect, but the way this piece is written reminds me distinctly of similar essays about WiFi sickness, MSG, and GMOs.
It identifies a "health risk", describes the mechanism in terms that sound very convincing, assigns numbers to its cause and effects, provides a table grading health risks of various products, all without linking to a single scientific study demonstrating that the effect is anything other than nocebo. The closest they come is a image of a table that refers to a few institutions that apparently did a study related to PWM (leaving it an exercise to the reader to find the studies they're supposedly referencing) and a link to a Wikipedia page which links to a Scientific American article which says:
> In 1989, my colleagues and I compared fluorescent lighting that flickered 100 times a second with lights that appeared the same but didn’t flicker. We found that office workers were half as likely on average to experience headaches under the non-flickering lights. No similar study has yet been performed for LED lights. But because LED flickering is even more pronounced, with the light dimming by 100% rather than the roughly 35% of fluorescent lamps, there’s a chance that LEDs could be even more likely to cause headaches.
I'm willing to entertain the idea that LED flicker is actually problematic, but I wish essays like this would be honest about the degree of confidence we have given the current state of the evidence. This piece instead takes it as a given that there's a problem, to the point where they confidently label devices on a scale of Low to Extremely High health risks.
mrob · 3h ago
There doesn't need to be a health risk for it to be annoying. I personally dislike PWM and I'll continue to personally dislike it even if it's proven safe. Fortunately it's easy to find non-flickering LED lights.
demosthanos · 3h ago
If the article said "I find PWM annoying" I wouldn't have commented like I did.
There is nothing anecdote about flickering in LED light causing health risks.
demosthanos · 3h ago
I am not questioning that certain types of flickering are harmful, so that there's an IEEE standard for how to safely use PWM does not contradict what I said.
What I'm asking for is for articles like this that cite numbers and provide tables purporting to quantify the degree of harm caused by various devices to point to where they're getting their numbers from or, if they can't do that, stop making up numbers and assigning things to "harm" scales that they invented themselves based on vibes.
Either there's a study showing that 246 Hz flickering poses "Extremely High" health risks or there isn't.
PaulHoule · 2h ago
Was it an astronomically high health risk to watch a TV set that flickers at 60 Hz or movies that flicker at 48 or 72 Hz? (It is 24 frames per second but you'd perceive a lot of flicker at that rate so the shutter has 2 or 3 blades)
NhanH · 2h ago
See my comment on the other reply.
> Either there's a study showing that 246 Hz flickering poses "Extremely High" health risks or there isn't.
They calculated it using the definition from the standard.
demosthanos · 2h ago
Can you please cite the page number where this definition exists? When I search for "extreme" in the standard that the other commenter links to I don't turn anything up, so I'm unclear where that classification is defined.
NhanH · 2h ago
31 and 32 (by the printed page number), in pdf it’s 42
demosthanos · 2h ago
That does not define the scale that they're using. That's a typical hazard analysis risk matrix which has two axes which can be converted into a 4-point scale (Low, Medium, Serious, High). Importantly, to do a risk assessment in the style of IEEE 1789's you have to identify the specific Hazards that you're analyzing, which TFA does not claim to be doing in that table, instead speaking vaguely of "health risks". IEEE 1789 does not provide a mechanism for evaluating "health risks" without specifying exactly which risks are being evaluated.
You can see on page 27 how this is meant to be used: it should produce a per-hazard matrix.
You might be thinking of Figure 18 on page 29, which does identify Low-risk and No-effect regions by Modulation % and Frequency, but that also does not claim to identify high-risk regions, it just identifies the regions we can be highly confident are safe. And importantly, as a sibling comment notes, TFA's table actually contradicts the line on Figure 18, labeling several devices as higher than Low even when they're squarely within the Low-Risk and No-Effect zones.
Kirby64 · 2h ago
The article contradicts the IEEE paper.
They list the 'Xiaomi 15 Ultra' as having a 'Moderately High' health risk, and cite it as having a 2.16 kHz PWM frequency at 30-75% modulation depth.
The IEEE article has recommended practices that state:
8.1.2.3 Example 3: PWM dimming
Using Figure 20, the recommended practice for PWM dimming at 100% modulation depth is that the frequency satisfies f > 1.25 kHz. This can also be derived using Recommended Practice 1 and solving 100% = 0.08×fFlicker. This level of flicker could help minimize the visual distractions such as the phantom array effects.
Seems like even at 100% mod depth, >1.25 kHz is just fine.
Also, the article does not seem to distinguish between modulation at reduced brightness, which the IEEE article calls out specifically as something that is unlikely to cause issues. E.g., movie theaters using film all flicker at 48 Hz and nobody complains about that.
Sure, PWM light can cause health risks for some people, in some contexts. But taking research out of context is bad science.
Do you genuinely believe the Pixel 7 and 8 Pro have an "extremely high health risk", in the context of what a lay person would understand?
Edit: I specify 'lay-person' because clearly this is an introductory blog post (or advertisement for Daylight Computer). If they want to use a more specific definition of health risk, then they better define it.
NhanH · 2h ago
The “very/moderate high” comes from the standard itself, which is quantified within the standard. In the context, it is about the probability of having issues, while the effect (mild to catastrophic) is another axis. Considering that they stick to the “official” wording and seeing the criticism, I am not even sure if they can change to a more “lay-person” friendly and be acceptable to all the critics.
The standard also linked to the researches during their discussion.
Please read it, instead of just randomly throw out things hoping that they supported your argument.
demosthanos · 2h ago
You can't just point people at a 60-page paywalled standard and say "the supporting evidence to my claim is somewhere in here, I pinky promise". You are the one making assertions, it's on you to prove that the standard actually does reflect the text of TFA. I'm not going to read the whole standard because I'm not the one making the argument and I can't be bothered doing the research needed to refute every piece of nonsense science that shows up on the internet. What I can do is point out when someone is making unsourced claims and insist that they provide their sources if they want to be taken seriously.
Cite the exact page number and quote that you claim justifies the assertion that 246 Hz PWM carries an "extremely high" health risk. Then we can talk.
NhanH · 2h ago
Look, they sourced their claims (quite literally, they put how they calculate, from which standard). And linking to the correct document is literally how scientific citation works — I replied the page to you above anyway.
If you want to redo the numbers and check if they fit the definition, please feel free to do so, but you will need to put some works in (since the flicker hz -> risk showing in the article is a computed value, you need to find the modulation value and plug it in too)
I understand your fight and your idea, I am just saying that in this specific instance, this is not a fight to be fought. The article is generally correct, and if you want to complain about the writing style or it being an ads, it’s up to you. But this is not the same situation with GMO stuffs
demosthanos · 2h ago
> Look, they sourced their claims (quite literally, they put how they calculate, from which standard).
No, they said that IEEE 1789 also uses Modulation % (which they've renamed Flicker %) to calculate risks. That is pointedly not the same thing as claiming that they used IEEE 1789's formulas.
You're reading their copy generously, but that doesn't usually pay with marketing copy. Articles like this always like to wave in the general direction of official-sounding sources while carefully refraining from actually claiming that they got their numbers from anywhere in particular.
I've got a couple bulbs from Waveform Lighting and they don't flicker, but I totally can tell the reds are off.
I really hate the LED transition. My building replaced all the outdoor lights with them, and now it's just too bright to sit on my stoop at night like used to be so common here in Brooklyn. My backyard neighbor put in an LED floodlight and now I have to buy blackout curtains. I drive rarely, but the oncoming headlights are blinding when I do. It's pretty depressing if I think about it too much.
I wonder if there's room to at least engage with the neighbor to talk about friendlier light options? You might also be able engage with these folks to see if there are efforts to improve the lighting in new York: https://darksky.org/
You could probably still reduce the flicker by either increasing the switching frequency or putting some kind of filter network between the switch and the load.
But I've also never lived in a house that has dimmers (they've all been old homes in the north eastern US) and I never use overhead lighting, so it's not something I need or would miss.
https://en.wikipedia.org/wiki/LED_tube#History
Medicine for depression, anxiety, insomnia...
it's nearly a closed loop; something i intuitively realized shortly after 2001/09/11 - by the end of that year i decided i would no longer have a "Television" attached to CATV/SAT/ANT service.
I'm not sure if i am correct, i haven't really dedicated a lot of time to getting the exact numbers, talking to psychologists and sociologists and the like. But two people i know had "breakdowns" (grippy sock) in the last month and both of them always have true crime on TV in the background or listen to true crime podcasts. Shortly after that happened i was listening to the moe facts podcast where Moe used the term "trauma based entertainment" and something clicked - Moe didn't mention "it's because of pharma ads" - that's my own input after having worked for the largest television "broadcast" company in the world, just long enough to see the advertiser "dinner".
> it's nearly a closed loop; something i intuitively realized shortly after 2001/09/11 - by the end of that year i decided i would no longer have a "Television" attached to CATV/SAT/ANT service.
Curiously this is about the same time I decided to give up on TV and radio as well.
"To understand why PWM bulbs have so much flicker, imagine them being controlled by a robot arm flicking the on/off switch thousands of times per second. When you want bright light, the robot varies the time so the switch is in the 'on' mode most of the time, and 'off' only briefly. Whereas when you want to dim the light, the robot arm puts the switch in 'off' most of the time and 'on' only briefly."
I am not aware of LED bulbs (and here I am talking about home lighting, not phones or laptops) that dim by shutting down some of the (multiple) LEDs.
Most home lighting bulbs appear to have several LED elements. A circuit could enable dimming by simply shutting some of them off — running the rest full-on. 50% dim would of course shut half the LEDs off. No PWM required.
Additionally, for bulbs that are used in regular household fixtures, they basically need a way to convert TRIAC chopped 50/60Hz AC into constant current... which makes things even more expensive. Smart bulbs that are supplied a constant non-chopped AC can do it easier, but it's still expensive to do DC dimming.
When I was in high school we were messing around with liquid nitrogen and overvolting LEDs and noticed the odd effect that the color of the LED would change if you overvolt it. It was years before I found out why
https://www.reddit.com/r/AskElectronics/comments/v28qbh/why_...
https://spectrum.ieee.org/a-definitive-explanation-for-led-d...
this is different than a bulb like hue etc that have the ability to dim themselves through whatever mechanism.
There are two ways to dim an LED: supply less current at the same voltage, or PWM dim it with a fast enough switching speed that you don't notice the flicker (this being slower than it needs to be is what the article is about). A current source is pretty easy to build, and doesn't flicker, but it does dissipate all the excess energy as heat. That's not what you want inside the dimmer switch in your wall, it can be quite a lot of heat and would be a fire hazard in such a confined area. It does work for things like photography lamps which can have exterior heat sinking.
And perceiveved brightness is equal to the peak of the PWM wave?
That image from courtesy Daylight Computer Company is consuming too much of my attention.
For OLED I remember reading that PWM dimming is necessary because DC dimming causes shifts in color/whitepoint.
Give me a nice candle.
Why do we use anonymity for that? What's gained and lost by that?
It identifies a "health risk", describes the mechanism in terms that sound very convincing, assigns numbers to its cause and effects, provides a table grading health risks of various products, all without linking to a single scientific study demonstrating that the effect is anything other than nocebo. The closest they come is a image of a table that refers to a few institutions that apparently did a study related to PWM (leaving it an exercise to the reader to find the studies they're supposedly referencing) and a link to a Wikipedia page which links to a Scientific American article which says:
> In 1989, my colleagues and I compared fluorescent lighting that flickered 100 times a second with lights that appeared the same but didn’t flicker. We found that office workers were half as likely on average to experience headaches under the non-flickering lights. No similar study has yet been performed for LED lights. But because LED flickering is even more pronounced, with the light dimming by 100% rather than the roughly 35% of fluorescent lamps, there’s a chance that LEDs could be even more likely to cause headaches.
I'm willing to entertain the idea that LED flicker is actually problematic, but I wish essays like this would be honest about the degree of confidence we have given the current state of the evidence. This piece instead takes it as a given that there's a problem, to the point where they confidently label devices on a scale of Low to Extremely High health risks.
There is nothing anecdote about flickering in LED light causing health risks.
What I'm asking for is for articles like this that cite numbers and provide tables purporting to quantify the degree of harm caused by various devices to point to where they're getting their numbers from or, if they can't do that, stop making up numbers and assigning things to "harm" scales that they invented themselves based on vibes.
Either there's a study showing that 246 Hz flickering poses "Extremely High" health risks or there isn't.
> Either there's a study showing that 246 Hz flickering poses "Extremely High" health risks or there isn't.
They calculated it using the definition from the standard.
You can see on page 27 how this is meant to be used: it should produce a per-hazard matrix.
You might be thinking of Figure 18 on page 29, which does identify Low-risk and No-effect regions by Modulation % and Frequency, but that also does not claim to identify high-risk regions, it just identifies the regions we can be highly confident are safe. And importantly, as a sibling comment notes, TFA's table actually contradicts the line on Figure 18, labeling several devices as higher than Low even when they're squarely within the Low-Risk and No-Effect zones.
They list the 'Xiaomi 15 Ultra' as having a 'Moderately High' health risk, and cite it as having a 2.16 kHz PWM frequency at 30-75% modulation depth.
The IEEE article has recommended practices that state:
8.1.2.3 Example 3: PWM dimming Using Figure 20, the recommended practice for PWM dimming at 100% modulation depth is that the frequency satisfies f > 1.25 kHz. This can also be derived using Recommended Practice 1 and solving 100% = 0.08×fFlicker. This level of flicker could help minimize the visual distractions such as the phantom array effects.
Seems like even at 100% mod depth, >1.25 kHz is just fine.
Also, the article does not seem to distinguish between modulation at reduced brightness, which the IEEE article calls out specifically as something that is unlikely to cause issues. E.g., movie theaters using film all flicker at 48 Hz and nobody complains about that.
Sure, PWM light can cause health risks for some people, in some contexts. But taking research out of context is bad science.
Do you genuinely believe the Pixel 7 and 8 Pro have an "extremely high health risk", in the context of what a lay person would understand?
Edit: I specify 'lay-person' because clearly this is an introductory blog post (or advertisement for Daylight Computer). If they want to use a more specific definition of health risk, then they better define it.
The standard also linked to the researches during their discussion.
Please read it, instead of just randomly throw out things hoping that they supported your argument.
Cite the exact page number and quote that you claim justifies the assertion that 246 Hz PWM carries an "extremely high" health risk. Then we can talk.
If you want to redo the numbers and check if they fit the definition, please feel free to do so, but you will need to put some works in (since the flicker hz -> risk showing in the article is a computed value, you need to find the modulation value and plug it in too)
I understand your fight and your idea, I am just saying that in this specific instance, this is not a fight to be fought. The article is generally correct, and if you want to complain about the writing style or it being an ads, it’s up to you. But this is not the same situation with GMO stuffs
No, they said that IEEE 1789 also uses Modulation % (which they've renamed Flicker %) to calculate risks. That is pointedly not the same thing as claiming that they used IEEE 1789's formulas.
You're reading their copy generously, but that doesn't usually pay with marketing copy. Articles like this always like to wave in the general direction of official-sounding sources while carefully refraining from actually claiming that they got their numbers from anywhere in particular.