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Lifetime isn't even my #1 concern with LED bulbs. It's strobing/flickering. I film all the LED bulbs I buy in slow motion at 240 fps with an Android phone, and

by mrb 8y ago

Lifetime isn't even my #1 concern with LED bulbs. It's strobing/flickering. I film all the LED bulbs I buy in slow motion at 240 fps with an Android phone, and play the movie back on a PC with mplayer using the dot(".") key to move frame by frame. Here is a shot I made comparing 2 brands of LED bulbs: https://youtu.be/QbenId_F2RQ https://youtu.be/QbenId_F2RQ (Edit: yeah you don't have to transfer to a PC, just playing back in slow motion on the phone will still show the effect quite well.) It's amazing how I find this way that most (but not all!) of LED bulbs flicker with a strobe effect at 120 Hz (frames alternate between bright and dim) because they have crappy power supply designs that fail to smooth the A/C voltage. As a result they flash one time during the positive phase and one time during the negative phase of the 60 Hz A/C mains frequency. I find this unacceptable. Although not too noticeable in normal conditions, a 120 Hz strobing light is definitely noticeable when your eyes move or track an object illuminated by the bulb. In my experience, Philips lightbulbs are one of the few brands that don't have this flaw because they take care of converting AC to a stable DC voltage internally. In fact they are advertised as such: https://www.amazon.com/dp/B07CFRCGKC https://www.amazon.com/dp/B07CFRCGKC "COMFORTABLE LIGHT: Our products meet strict test criteria including flicker, strobe, glare and color rendition to ensure they meet EyeComfort requirements"

telchar 8y ago
Perhaps dimmable LED bulbs would be better in that regard? The LED dimmers on the market use a very high rate PWM (afaik) to prevent/minimize flickering at low brightness. I would guess that the dimmable bulbs are designed to work well with intermittent power and so wouldn't have the same problem. Of course it's still hit or miss, compatibility between bulbs and dimmers seems to be very hard to judge without testing these days.
- masklinn 8y ago
  The bulb they link are listed as dimmable (flicker-free silent dimming) aside from the part they quoted.
- mrb 8y ago
  In my experience, dimmable bulbs are no better. Most of them still suffer from the 120 Hz strobing effect. That's because even though they might PWM at 1-10 kHz to control the dimming function, when A/C voltage crosses zero, the "on" state of the PWM can still be a lot dimmer than the "on" state during the A/C voltage peak.
  - telchar 8y ago
    I would think a good LED would need something like a full wave rectifier with a good smoothing circuit to minimize flicker. I bet a lot of the bulbs on the market cheap out on the electronics though.
- manmal 8y ago
  Dimmable LEDs are not automatically flicker-free. My father had very cheap dimmable ones, and I complained at every visit about the strobe effect until he bought flicker-free ones. Most dimmers work via pulse width modulation [1], i.e. the power supply is switched on/off in a different interval (more off time means lower brightness). A true flicker-free dimmed LED has to be dimmed in an analog way (probably only feasible for "dumb" light bulbs). PWM of 20kHz or something might also work, but who knows what that does to brain waves. 1: https://www.waveformlighting.com/film-photography/an-introduction-to-flicker-free-led-strip-dimming https://www.waveformlighting.com/film-photography/an-introdu...
  - pistachiopro 8y ago
    I can't find the source right now, but I read that the fastest cells in the visual pathway can respond at a bit under 500Hz. Part of the reason the ieee suggests a minimum PWM frequency of 3000Hz is, for signal processing reasons I don't fully understand, that's the highest frequency the brain could likely detect, given 500Hz "sampling hardware."
    - manmal 8y ago
      You might still get strobe effects where your 500hz sensing nerves eg get a 400hz signal from a 20khz source.
- sosuke 8y ago
  My oven has a high / low switch for the LED lights and I can't have it on low because the strobe/flicker drives me nuts.
manmal 8y ago
I only buy Philips bulbs for this very reason, or from brands that advertise being flicker-free. With iphones, slow motion mode also makes the flicker very visible without the need to transfer to a PC. Visible light impulses influence brain wave patterns (e.g. [1]), and it might not be beneficial to look at pulsed light with a frequency that is not well researched. Same thing with screens, most LEDs are dimmed with pulse width modulation [2], so they flicker at most brightness levels except the very brightest one. Some iPhone X users claim they get a headache when looking at the phone at the lowest brightness setting (OLED is even worse in that regard than LED, IIRC). 1: https://clinicaltrials.gov/ct2/show/NCT03657745 https://clinicaltrials.gov/ct2/show/NCT03657745 2: https://www.eetimes.com/document.asp?doc_id=1281013 https://www.eetimes.com/document.asp?doc_id=1281013
- petre 8y ago
  I had a small bag of Chinese position light LED T10 lamps for my car my dad had given me. I would change them every three to five months because the LEDs would burn out. Getting sick of sticking my hand in narrow spaces to replace the lamps, I ordered two Philips Xtreme Vision 4000K T10 LED lights. They've beeen running flawlessly more than a year now.
- dombesz 8y ago
  Very good points here, I would add that 99% of the monitors are also flickering when you dim their ligth. This is why i started using the iris[1] app on my laptop. Keeping the brightness at 100% in the hardware settings will eliminate the flicker, then iris dims the lights from your graphic card. I can work without eye oain thanks to this method. - [1] https://iristech.co https://iristech.co
  - manmal 8y ago
    Oh, I had been looking for something like this for the desktop, thanks for mentioning it! On iOS there’s a setting buried deeply in accessibility settings, I think it’s called white point correction.
- ksec 8y ago
  >Some iPhone X users claim they get a headache when looking at the phone at the lowest brightness setting (OLED is even worse in that regard than LED, IIRC). And on iPhone XS this is even worst. I wonder if there are any solution to PWM problem.
slow_donkey 8y ago
Never even thought about this problem, thanks for bringing it up
sosuke 8y ago
I'm really happy to see you post this. Everyone else I've brought it up too just says I'm crazy. I might be crazy but not about the damn flickering/strobe. Especially when my dog bounces around it looks like she is in a strobe light. I did a couple of videos of it just to "prove" it in some fashion. https://www.youtube.com/watch?v=DddB_0QrV_8 https://www.youtube.com/watch?v=DddB_0QrV_8
- arm 8y ago
  You’re definitely not crazy. HN also had a big discussion about it two months ago in this¹ thread as well. ―――――― ¹ — https://news.ycombinator.com/item?id=18644590 https://news.ycombinator.com/item?id=18644590
- ksec 8y ago
  The people who are crazy enough to think they can change the world are the ones who do.
- xiconfjs 8y ago
  I use a salt shaker and pour salt onto a plate - if I can make out single falling grain of salt on the way to the plate, I know this light source is not healthy for humans.
  - jfengel 8y ago
    Hang on, how does that work?
simcop2387 8y ago
What I've found to help weed out the worst of the worst is to only buy dimmable versions of the bulbs. They cost more but because they have to support dimming they're almost required to have a better power supply to handle the usual triac based control that most dimmers have.
- dpwm 8y ago
  Not sure this always holds. The worst bulbs I've personally seen for flicker were dimmable ones. The non-dimmable variant from the same range had no noticable flicker. Price paid also seems to be no indicator of quality – I've had premium LED bulbs from major makes, bought from a reputable wholesaler, that have died after 6 months within days of each other. I've had cheap no-name imports that have lasted years and had no flicker.
  - Moru 8y ago
    Yes, the dimmable has been the worst for me so far, they just make them flicker more to give less light.
  - unicornporn 8y ago
    Confirmed. Have dimmable at work and home and they flicker like crazy.
  - patal 8y ago
    A lot of "dimmable" LEDs are actually shifting the flicker pattern to dim the light (shorter on phases). This is for LEDs where the user dims per remote control. OP was talking about the older "legacy" dimming, where you have a wall-mounted knob that reduces the current. Works well with incandescent bulbs. But only few LEDs support this. If they do, their internal power converter likely won't flicker, because of their more thought-out converter? However, there are also LEDs that support legacy dimming, but again translate less current into different flicker patterns...
    - thinkling 8y ago
      I've been trying to switch to all-LED in a home with lots of legacy dimmers and it's been painful. Even on circuits where I've replaced older dimmers with new Lutron CFL/LED dimmers, I get flicker. In other places I don't have dimmers but have low-voltage (12V) cans. Lots of flicker issues there too, presumably due to the 120->12V transformer at the can. And then I have a light fixture that's both dimmed and a custom 12V setup. I've given up on finding a working dimmer/LED bulb (MR16 GU5.3) there. Probably need new 12V transformers?
broabprobe 8y ago
We need IEEE PAR1789 bulbs! The department of energy has a great presentation on LED flicker and this IEEE standard for better bulbs, https://www.energy.gov/sites/prod/files/2015/05/f22/miller%2Blehman_flicker_lightfair2015.pdf https://www.energy.gov/sites/prod/files/2015/05/f22/miller%2...
8ytecoder 8y ago
Philips has some solid products. Our old television used to be Philips and it lasted a full decade and a half - we only got rid of it to get an LED TV. Most of our light bulbs have been Philips all my life and they have generally lasted a good while better than other brands we have used.
pistachiopro 8y ago
I completely agree, flicker has been the most distracting part of switching to LEDs, for me. Here are two good sites that posted graphs of light intensity over time for a bunch of different bulbs: http://www.ledbenchmark.com/ http://www.ledbenchmark.com/ http://sle.se/michael/led/ http://sle.se/michael/led/ (Swedish) Unfortunately, they both stopped updating around 2015. Anyone know of similar sources for more recent bulbs?
- arm 8y ago
  In the huge HN thread here¹, yeutterg mentioned² their Bedtime Bulb: > “I am on a mission to make lighting healthy. That's why I made Bedtime Bulb: https://bedtimebulb.com/ https://bedtimebulb.com/ It has the lowest flicker I've ever seen in a bulb form factor—even less than those claiming to be "flicker-free."” In addition to that, a few other database sites that test for flicker were mentioned here³. ―――――― ¹ — https://news.ycombinator.com/item?id=18644590 https://news.ycombinator.com/item?id=18644590 ² — https://news.ycombinator.com/item?id=18650624 https://news.ycombinator.com/item?id=18650624 ³ — https://news.ycombinator.com/item?id=18646409 https://news.ycombinator.com/item?id=18646409
  - yeutterg 8y ago
    I've tested a bunch of bulbs for flicker with a handheld flicker meter and with a photodiode connected to an oscilloscope. It's funny that some of the bulbs out there claiming to be "healthy" have terrible flicker. One product from Soraa was flickering at over 50%, almost as bad as the cheapest/worst LED bulbs you can buy. I don't have a database, but I can say that most (but not all) filament designs are terrible for flicker--ours is an exception. Philips products seem to have gotten worse in quality over time, probably to remain competitive, but they are better than the worst. Ikea's stuff is pretty good overall. I don't have a consistent recommendation for low-flicker general lighting right now, as every brand has good and bad products.
    - pistachiopro 8y ago
      Thanks to GP for the links, I completely missed that previous thread! And, yeah, I tried that Soraa healthy bulb, and it was shockingly bad, given how it was advertised. Even the regular Soraa bulbs were disappointingly flickery, though less so. Also, just looking at the pattern it makes on my phone's rolling shutter, the wave is quite saw-toothed, and I wonder if that makes it worse? I have some Ikea candelabra bulbs which were always pleasant, and I was surprised to see they also left quite a visible flicker pattern on my phone, though much more sinusoidal/smoother. It's a shame about the flicker in the Soraa bulbs, since the colors really did seem nice.
Jedd 8y ago
A metal working friend told me recently that in Australia we're not meant / allowed to use fluorescent lights above lathes, as the flicker can disguise movement. This is slightly worrying.
- masklinn 8y ago
  Yeah gas discharge lamps (CFL, neons, halides) will flicker at twice the mains' frequency on a single-phase circuit, makes it very dangerous to use them as e.g. factory lighting. You can mitigate that by using 3-phase power supplies, high-frequency controller, or by supplementing the basic lighting with incandescent bulbs around machinery. The stroboscopic effect is really fun right until you're in a place with lots of moving parts at a multiple of the strobe frequency. OTOH it's also used to fine-tune engine timing and such: set a stroboscope at a fraction of the frequency you want, the engine is properly tuned when everything looks completely stopped. Makes it very easy to notice mistiming.
  - wlesieutre 8y ago
    Some turntables include a strobing light and rings of dots around the edge for different speeds. If it's spinning at the correct speed the corresponding dots will stand still.
  - Jedd 8y ago
    Absolutely - the way he described it sounded like a horrendous accident waiting to happen, especially for smaller / home shops where the operator may not be aware of the problem. He was under the expectation that LEDs solved this problem, though he is using drop-in LED tubes that may have some better persistence through the off-cycles. I do some occasional wood-turning, but usually augmented with ambient daylight - along with the dubious safety advantage of having a very noisy electric motor. Plus I'm old enough to have used a timing light hanging off a distributor on my first car. Try explaining that to the kids of today. ; )
    - afandian 8y ago
      A friend of my mother's lost half a finger to a strobing light and a circular saw. It does happen!
GordonS 8y ago
I just went and tried to find a bright (1000-1500 lumens) Philips LED bulb with a cool temperature (3500-4500)... but it seems every Philips LED bulb is "warm white"* :/ That's fine for a living room, but not what I want in my home office, kitchen or bathroom. * at least in the UK
amatecha 8y ago
Yeah I can immediately tell when an area is illuminated by LED lights when I spot the strobing/flickering as I move my eyes and the saccade reveals the slow frequency of the light dispersal (or however it would be worded). It's super jarring and can be a bit disorienting.
ricardobeat 8y ago
On an iPhone - at least the 6S I have - you don’t even need to record a video. Just switching to slow motion in the camera app will instantly show you flicker in the live preview, I assume because it’s interpolating frames from the 120hz input.
ahartmetz 8y ago
Shaking a hand with fingers spread out somehow works to spot flicker. If the light source flickers, you see oddly sharp finger positions in the air. It's not the most sensitive or easy to interpret method.
- matmann2001 8y ago
  The John Cena method?
- Arbalest 8y ago
  I remember doing this with CRTs
  - JohnBooty 8y ago
    I calculated the airspeed of a rubber band this way once! My coworker shot a rubber band in my direction. I noticed three “shadows” of the rubber band as it passed by the CRT. The CRT was a 17” running at 60hz. The rubber band sailed past in the span of about 2 screen refreshes, so it traveled that distance in 2/60 of a second. Distance was easy to calculate by the Pythagorean theorem or by holding a ruler to the screen, I forget which.
Moru 8y ago
I usually just move my phone really close to the lightbulb and watch the live camera view. At a certain distance/angle you can usually see the flicker as banding across the screen. I saw a test in a Swedish newspaper lately that showed IKEA's cheapest lightbulbs as one of the less flickery ones in the test. IKEA art.nr 303.887.64. So much for the price to guide you.
- Tsubasachan 8y ago
  Bought an IKEA led lightbulb for €3 and the packaging says it should last 15000 hours. Not bad really. LED lights are alright. Lots of people think that everything used to be better but my memory is too good to fall for that trap.
TheSpiceIsLife 8y ago
LED flicker could prove harmful or fatal if you work with anything that rotates or reciprocates. The rotating / reciprocating mass may appear stationary at some RPM. Just a reminder to only ever use incandescent or halogen lights around machinery you can touch while in operation: drills, lathes, mills, slotting machines, etc.
- handzbagz 8y ago
  Just how likely is this to happen though, it would have to be the only light source and be flickering with exactly the same frequency as the machinery is traveling at (which i assume for most devices varies a lot). Not saying it can't happen but it does seem stupidly hard to achieve.
  - simcop2387 8y ago
    It doesn't have to be going the exact same speed, a multiple would do the trick too. It can also be dangerous if it's close to the same rate since it can then look like it's going slower even if not stopped.
    - TheSpiceIsLife 8y ago
      Or the rotating / reciprocating object may appear to be rotating / reciprocating slowly in the opposite direction. Even after 20 years in the metal fabrication industry that scenario still spooks me.
  - deleted 8y ago
    [deleted]
  - icelancer 8y ago
    This is uncommon but not rare. Have you ever seen wheel blur or other artifacting of such? It's very easy to make happen artificially under controlled conditions which means it can't be that hard to happen accidentally. Edited to add: Have you ever heard of a timing light for an engine? This works exactly the way you are describing.
arm 8y ago
Have to mention this¹ big HN thread from 2 months ago with lots of discussion about that exact issue. ―――――― ¹ — https://news.ycombinator.com/item?id=18644590 https://news.ycombinator.com/item?id=18644590
MPSimmons 8y ago
I can spot a Cadillac or GMC vehicle on the road a mile behind it from the flicker of the taillights. It's terrible.
- timbit42 8y ago
  Why do they flicker? Are they AC powered?
  - bradyd 8y ago
    You can dim LEDs by turning them on and off really fast using a process known as pulse width modulation (PWM). Ideally for something like brake lights you would use a constant current driver to control the light level to prevent flickering. I don't know why GM is using PWM, but I'm guessing they just use a cheap control circuit. I really hate their LED tail lights. Just moving your eyes from side to side is enough to easily see the flashing.
    - kurthr 8y ago
      Also, due to leakage for large LEDs they are more efficient at higher current. That means that for a given power, you're better off driving them at a higher current for a shorter duration. You can increase the effective luminance without violating the power spec.
- yeutterg 8y ago
  Agreed. Most car manufacturers' LEDs flicker (just look at any slow-motion video, such as those on Top Gear or The Grand Tour), but GM's are at a much lower frequency that is visible if the vehicle is in motion, or you are in motion.
  - nitrogen 8y ago
    I always wondered if anyone ever tried to encode information into the flicker pattern of LED tail lights. I can think of a lot of uses, good and bad.
14 8y ago
This concerns me. About a year ago I went onto a website and ordered 56 led bulbs for my entire house and thought I got a fairly good deal. They worked seemingly well but my eyes always felt strained when under them. Just took my iphone and can definitely see the flicker with slow motion. And when I look at items as I move my head across the room I feel like I can see it as you say and never really knew what I was experiencing before. As someone who always talks about having sensitive eyes to light I am definitely not happy about this and am now thinking about buying flicker free bulbs. Thanks for sharing.
- brachi 8y ago
  Next time, a good resource is https://ledstrain.org/ https://ledstrain.org/. I found it here in HN and is quite informative for makign decisions on what to buy.
dingo_bat 8y ago
This is why there's such a price gap between hue bulbs and everything else.
pishpash 8y ago
I have electric heating and in the winter there is no energy benefit at all from LED bulbs. I want my incandescents back. They really feel comfortable in a way I can't explain.
- copperx 8y ago
  They really do. I placed an incandescent on a floor lamp to use it for reading, and it's now the most pleasant light on my house by far. But it gives me anxiety to leave it on for a long period of time because I know it's a huge waste of energy. The second best are my Phillips SceneSwitches, which I really love but don't come in 100w.
copperx 8y ago
Ah! I'm glad someone found the same thing as I did regarding Phillips bulbs. Here's my old post: https://news.ycombinator.com/item?id=18645237 https://news.ycombinator.com/item?id=18645237
tiff_seattle 8y ago
My Philips Hue bulbs visibly flicker when they are dimmed, but not when they are at full brightness. I never had that problem with the old style bulbs. I wonder if that could be fixed with a firmware update?
- yeutterg 8y ago
  Theoretically, they could, but I don't think Philips really has a financial incentive to update anything that "already works"
kurthr 8y ago
Have you tried this with incandescent bulbs? They flicker at 120Hz too... since they are P=I^2R and driven directly from 60Hz lines. I don't know the amplitude variation that bothers you, but then I don't mind LED bulbs. Of course it's not the LEDs that do this but the cheap AC-DC conversion bridge rectifier.
- mgleason_3 8y ago
  Yeah, but because incandescent bulb filament's retains enough heat to continue to glow between peaks, their flickering is almost negligible - especially compared to poorly designed LED and CF bulbs.
mixmastamyk 8y ago
Interesting, I used to be very bothered by computer CRT monitors set at 60hz refresh and bright backgrounds. I'd go into the Windows control panel (most often) and increase it as far as it would go at the given resolution. Through trial and error I found that 72hz was acceptable/ok and 90hz and above was great. Other folks generally didn't notice, but sometimes could if I showed them to look sideways etc. This must explain why I've never knowingly been bothered by 120hz LED flicker, it is below my ability to consciously notice. Curious, I took a look at several bulbs, with the mobile at 240fps trick described elsewhere. A new Feit dimmable, new Ecosmart non, a several year old Ikea, and a no-name CFL. All showed flicker except the CFL. All the LEDs flickered, but the amplitude was larger on the ecosmart. Feit and Ikea had a small amplitude. Perhaps they are putting half the LEDs out of phase to get the smaller amplitude, or they should?
- mixmastamyk 8y ago
  Small correction, the CFL did have some flicker, just small enough I didn't notice on first look.
voycey 8y ago
Our WeWork has them in the kitchens - I feel like I'm drunk whenever I am in there!
kuon 8y ago
Yes, I also have the flickering issue with some LEDs, and I can confirm that (to my eye) the philips LEDs I bought do not flicker. I also have a few OSRAM LEDs that don't flicker.
0x70dd 8y ago
I noticed the same thing when I was playing the guitar. The constant flickering combined with a vibrating string at a high frequency produces a nice looking effect [1], which can be observed with a naked eye (unlike the one in the video). [1] https://www.youtube.com/watch?v=ttgLyWFINJI https://www.youtube.com/watch?v=ttgLyWFINJI
Cthulhu_ 8y ago
I was in a hotel room a while ago which had some seriously flickering LED lights, just everywhere; moving around you could definitely see it. Wasn't pleasant.
BuildTheRobots 8y ago
I'm surprised no one has mentioned hte rise of flickering LEDs on cars - though I think in this case it's caused by PWM dimming. I mean, it looks absolutely fine as long as the light source and viewer are both static - just a shame vehicles tend to be moving :(
- graycrow 8y ago
  I don't get why DLR LEDs needs PWM at all. It 100% can be done without, even with smooth light distribution.
consp 8y ago
Cheap brands generally use some form of capacitive dropper scheme. These result in the 120/100Hz flickering but is cheap to produce as very little components are needed (X2 class capacitor, maybe some current limiting resistor(s) and a discharge resistor, bridge rectifier, or even skip the rectifier altogether). They are not to be used with a dimmer. Some info on them [1] The switch-mode power supplies in proper lamps get the stuff done way better and there will be no noticeable flicker. Maybe in the order of several kHz in ripple which you cannot see. Also; cheap off brands (looking at you china) sometimes have caps rated at 250V which is far from the peak mains rate of about 320V (in 220/230V countries). [1] https://www.powerelectronictips.com/whats-stuff-capacitive-power-supplies-leds/ https://www.powerelectronictips.com/whats-stuff-capacitive-p...
apexalpha 8y ago
+1 for Philips bulbs. Lights is something that I used to cheap out on but no more. Not buying Philips bulbs is definitely 'penny wise, pound foolish'. Also, Philips Hue!
moftz 8y ago
I bought some LED string lights for my bedroom because they were cheap. They turned out to be incredibly annoying due to the 60Hz flickering. Staring at them, it wasn't noticeable but the moment you moved your head or moved something quickly you could see the strobe effect. I trashed them and bought some incandescent lights.
TrueGeek 8y ago
I tried this with my office lamps and saw the flickering so I bought the Philips bulbs you linked to. They just arrived and I filmed them but they also show the flickering when filmed on an iPhone in slow-mo mode. Do I need to buy a specific model of Philips bulbs? Or is my Ikea lamp the culprit now? I paid a ton of money for a certified flicker free monitor so I'm very keen on making sure the lamps are flicker free as well.
rincebrain 8y ago
You say "don't have this problem", but given sufficiently unstable mains input, the Philips bulbs too will do this. Source: I just had a problem with a malfunctioning light switch (not even a dimming switch, a plain two-state switch) wherein sometimes it would poorly complete the circuit, and one bulb out of the four on the circuit would start oscillating on and off. (If you removed the one bulb, another would start. If you plugged the first bulb back in, in the original slot or another, it would happen to the first bulb only.)

by mrb 8y ago

telchar 8y ago

Perhaps dimmable LED bulbs would be better in that regard? The LED dimmers on the market use a very high rate PWM (afaik) to prevent/minimize flickering at low brightness. I would guess that the dimmable bulbs are designed to work well with intermittent power and so wouldn't have the same problem. Of course it's still hit or miss, compatibility between bulbs and dimmers seems to be very hard to judge without testing these days.

masklinn 8y ago
The bulb they link are listed as dimmable (flicker-free silent dimming) aside from the part they quoted.
mrb 8y ago
In my experience, dimmable bulbs are no better. Most of them still suffer from the 120 Hz strobing effect. That's because even though they might PWM at 1-10 kHz to control the dimming function, when A/C voltage crosses zero, the "on" state of the PWM can still be a lot dimmer than the "on" state during the A/C voltage peak.
- telchar 8y ago
  I would think a good LED would need something like a full wave rectifier with a good smoothing circuit to minimize flicker. I bet a lot of the bulbs on the market cheap out on the electronics though.
manmal 8y ago
Dimmable LEDs are not automatically flicker-free. My father had very cheap dimmable ones, and I complained at every visit about the strobe effect until he bought flicker-free ones. Most dimmers work via pulse width modulation [1], i.e. the power supply is switched on/off in a different interval (more off time means lower brightness). A true flicker-free dimmed LED has to be dimmed in an analog way (probably only feasible for "dumb" light bulbs). PWM of 20kHz or something might also work, but who knows what that does to brain waves. 1: https://www.waveformlighting.com/film-photography/an-introduction-to-flicker-free-led-strip-dimming https://www.waveformlighting.com/film-photography/an-introdu...
- pistachiopro 8y ago
  I can't find the source right now, but I read that the fastest cells in the visual pathway can respond at a bit under 500Hz. Part of the reason the ieee suggests a minimum PWM frequency of 3000Hz is, for signal processing reasons I don't fully understand, that's the highest frequency the brain could likely detect, given 500Hz "sampling hardware."
  - manmal 8y ago
    You might still get strobe effects where your 500hz sensing nerves eg get a 400hz signal from a 20khz source.
sosuke 8y ago
My oven has a high / low switch for the LED lights and I can't have it on low because the strobe/flicker drives me nuts.

manmal 8y ago

I only buy Philips bulbs for this very reason, or from brands that advertise being flicker-free. With iphones, slow motion mode also makes the flicker very visible without the need to transfer to a PC. Visible light impulses influence brain wave patterns (e.g. [1]), and it might not be beneficial to look at pulsed light with a frequency that is not well researched. Same thing with screens, most LEDs are dimmed with pulse width modulation [2], so they flicker at most brightness levels except the very brightest one. Some iPhone X users claim they get a headache when looking at the phone at the lowest brightness setting (OLED is even worse in that regard than LED, IIRC). 1: https://clinicaltrials.gov/ct2/show/NCT03657745 https://clinicaltrials.gov/ct2/show/NCT03657745 2: https://www.eetimes.com/document.asp?doc_id=1281013 https://www.eetimes.com/document.asp?doc_id=1281013

petre 8y ago
I had a small bag of Chinese position light LED T10 lamps for my car my dad had given me. I would change them every three to five months because the LEDs would burn out. Getting sick of sticking my hand in narrow spaces to replace the lamps, I ordered two Philips Xtreme Vision 4000K T10 LED lights. They've beeen running flawlessly more than a year now.
dombesz 8y ago
Very good points here, I would add that 99% of the monitors are also flickering when you dim their ligth. This is why i started using the iris[1] app on my laptop. Keeping the brightness at 100% in the hardware settings will eliminate the flicker, then iris dims the lights from your graphic card. I can work without eye oain thanks to this method. - [1] https://iristech.co https://iristech.co
- manmal 8y ago
  Oh, I had been looking for something like this for the desktop, thanks for mentioning it! On iOS there’s a setting buried deeply in accessibility settings, I think it’s called white point correction.
ksec 8y ago
>Some iPhone X users claim they get a headache when looking at the phone at the lowest brightness setting (OLED is even worse in that regard than LED, IIRC). And on iPhone XS this is even worst. I wonder if there are any solution to PWM problem.

slow_donkey 8y ago

Never even thought about this problem, thanks for bringing it up

sosuke 8y ago

I'm really happy to see you post this. Everyone else I've brought it up too just says I'm crazy. I might be crazy but not about the damn flickering/strobe. Especially when my dog bounces around it looks like she is in a strobe light. I did a couple of videos of it just to "prove" it in some fashion. https://www.youtube.com/watch?v=DddB_0QrV_8 https://www.youtube.com/watch?v=DddB_0QrV_8

arm 8y ago
You’re definitely not crazy. HN also had a big discussion about it two months ago in this¹ thread as well. ―――――― ¹ — https://news.ycombinator.com/item?id=18644590 https://news.ycombinator.com/item?id=18644590
ksec 8y ago
The people who are crazy enough to think they can change the world are the ones who do.
xiconfjs 8y ago
I use a salt shaker and pour salt onto a plate - if I can make out single falling grain of salt on the way to the plate, I know this light source is not healthy for humans.
- jfengel 8y ago
  Hang on, how does that work?

simcop2387 8y ago

What I've found to help weed out the worst of the worst is to only buy dimmable versions of the bulbs. They cost more but because they have to support dimming they're almost required to have a better power supply to handle the usual triac based control that most dimmers have.

dpwm 8y ago
Not sure this always holds. The worst bulbs I've personally seen for flicker were dimmable ones. The non-dimmable variant from the same range had no noticable flicker. Price paid also seems to be no indicator of quality – I've had premium LED bulbs from major makes, bought from a reputable wholesaler, that have died after 6 months within days of each other. I've had cheap no-name imports that have lasted years and had no flicker.
- Moru 8y ago
  Yes, the dimmable has been the worst for me so far, they just make them flicker more to give less light.
- unicornporn 8y ago
  Confirmed. Have dimmable at work and home and they flicker like crazy.
- patal 8y ago
  A lot of "dimmable" LEDs are actually shifting the flicker pattern to dim the light (shorter on phases). This is for LEDs where the user dims per remote control. OP was talking about the older "legacy" dimming, where you have a wall-mounted knob that reduces the current. Works well with incandescent bulbs. But only few LEDs support this. If they do, their internal power converter likely won't flicker, because of their more thought-out converter? However, there are also LEDs that support legacy dimming, but again translate less current into different flicker patterns...
  - thinkling 8y ago
    I've been trying to switch to all-LED in a home with lots of legacy dimmers and it's been painful. Even on circuits where I've replaced older dimmers with new Lutron CFL/LED dimmers, I get flicker. In other places I don't have dimmers but have low-voltage (12V) cans. Lots of flicker issues there too, presumably due to the 120->12V transformer at the can. And then I have a light fixture that's both dimmed and a custom 12V setup. I've given up on finding a working dimmer/LED bulb (MR16 GU5.3) there. Probably need new 12V transformers?

broabprobe 8y ago

We need IEEE PAR1789 bulbs! The department of energy has a great presentation on LED flicker and this IEEE standard for better bulbs, https://www.energy.gov/sites/prod/files/2015/05/f22/miller%2Blehman_flicker_lightfair2015.pdf https://www.energy.gov/sites/prod/files/2015/05/f22/miller%2...

8ytecoder 8y ago

Philips has some solid products. Our old television used to be Philips and it lasted a full decade and a half - we only got rid of it to get an LED TV. Most of our light bulbs have been Philips all my life and they have generally lasted a good while better than other brands we have used.

pistachiopro 8y ago

I completely agree, flicker has been the most distracting part of switching to LEDs, for me. Here are two good sites that posted graphs of light intensity over time for a bunch of different bulbs: http://www.ledbenchmark.com/ http://www.ledbenchmark.com/ http://sle.se/michael/led/ http://sle.se/michael/led/ (Swedish) Unfortunately, they both stopped updating around 2015. Anyone know of similar sources for more recent bulbs?

arm 8y ago
In the huge HN thread here¹, yeutterg mentioned² their Bedtime Bulb: > “I am on a mission to make lighting healthy. That's why I made Bedtime Bulb: https://bedtimebulb.com/ https://bedtimebulb.com/ It has the lowest flicker I've ever seen in a bulb form factor—even less than those claiming to be "flicker-free."” In addition to that, a few other database sites that test for flicker were mentioned here³. ―――――― ¹ — https://news.ycombinator.com/item?id=18644590 https://news.ycombinator.com/item?id=18644590 ² — https://news.ycombinator.com/item?id=18650624 https://news.ycombinator.com/item?id=18650624 ³ — https://news.ycombinator.com/item?id=18646409 https://news.ycombinator.com/item?id=18646409
- yeutterg 8y ago
  I've tested a bunch of bulbs for flicker with a handheld flicker meter and with a photodiode connected to an oscilloscope. It's funny that some of the bulbs out there claiming to be "healthy" have terrible flicker. One product from Soraa was flickering at over 50%, almost as bad as the cheapest/worst LED bulbs you can buy. I don't have a database, but I can say that most (but not all) filament designs are terrible for flicker--ours is an exception. Philips products seem to have gotten worse in quality over time, probably to remain competitive, but they are better than the worst. Ikea's stuff is pretty good overall. I don't have a consistent recommendation for low-flicker general lighting right now, as every brand has good and bad products.
  - pistachiopro 8y ago
    Thanks to GP for the links, I completely missed that previous thread! And, yeah, I tried that Soraa healthy bulb, and it was shockingly bad, given how it was advertised. Even the regular Soraa bulbs were disappointingly flickery, though less so. Also, just looking at the pattern it makes on my phone's rolling shutter, the wave is quite saw-toothed, and I wonder if that makes it worse? I have some Ikea candelabra bulbs which were always pleasant, and I was surprised to see they also left quite a visible flicker pattern on my phone, though much more sinusoidal/smoother. It's a shame about the flicker in the Soraa bulbs, since the colors really did seem nice.

Jedd 8y ago

A metal working friend told me recently that in Australia we're not meant / allowed to use fluorescent lights above lathes, as the flicker can disguise movement. This is slightly worrying.

masklinn 8y ago
Yeah gas discharge lamps (CFL, neons, halides) will flicker at twice the mains' frequency on a single-phase circuit, makes it very dangerous to use them as e.g. factory lighting. You can mitigate that by using 3-phase power supplies, high-frequency controller, or by supplementing the basic lighting with incandescent bulbs around machinery. The stroboscopic effect is really fun right until you're in a place with lots of moving parts at a multiple of the strobe frequency. OTOH it's also used to fine-tune engine timing and such: set a stroboscope at a fraction of the frequency you want, the engine is properly tuned when everything looks completely stopped. Makes it very easy to notice mistiming.
- wlesieutre 8y ago
  Some turntables include a strobing light and rings of dots around the edge for different speeds. If it's spinning at the correct speed the corresponding dots will stand still.
- Jedd 8y ago
  Absolutely - the way he described it sounded like a horrendous accident waiting to happen, especially for smaller / home shops where the operator may not be aware of the problem. He was under the expectation that LEDs solved this problem, though he is using drop-in LED tubes that may have some better persistence through the off-cycles. I do some occasional wood-turning, but usually augmented with ambient daylight - along with the dubious safety advantage of having a very noisy electric motor. Plus I'm old enough to have used a timing light hanging off a distributor on my first car. Try explaining that to the kids of today. ; )
  - afandian 8y ago
    A friend of my mother's lost half a finger to a strobing light and a circular saw. It does happen!

GordonS 8y ago

I just went and tried to find a bright (1000-1500 lumens) Philips LED bulb with a cool temperature (3500-4500)... but it seems every Philips LED bulb is "warm white"* :/ That's fine for a living room, but not what I want in my home office, kitchen or bathroom. * at least in the UK

amatecha 8y ago

Yeah I can immediately tell when an area is illuminated by LED lights when I spot the strobing/flickering as I move my eyes and the saccade reveals the slow frequency of the light dispersal (or however it would be worded). It's super jarring and can be a bit disorienting.

ricardobeat 8y ago

On an iPhone - at least the 6S I have - you don’t even need to record a video. Just switching to slow motion in the camera app will instantly show you flicker in the live preview, I assume because it’s interpolating frames from the 120hz input.

ahartmetz 8y ago

Shaking a hand with fingers spread out somehow works to spot flicker. If the light source flickers, you see oddly sharp finger positions in the air. It's not the most sensitive or easy to interpret method.

matmann2001 8y ago
The John Cena method?
Arbalest 8y ago
I remember doing this with CRTs
- JohnBooty 8y ago
  I calculated the airspeed of a rubber band this way once! My coworker shot a rubber band in my direction. I noticed three “shadows” of the rubber band as it passed by the CRT. The CRT was a 17” running at 60hz. The rubber band sailed past in the span of about 2 screen refreshes, so it traveled that distance in 2/60 of a second. Distance was easy to calculate by the Pythagorean theorem or by holding a ruler to the screen, I forget which.

Moru 8y ago

I usually just move my phone really close to the lightbulb and watch the live camera view. At a certain distance/angle you can usually see the flicker as banding across the screen. I saw a test in a Swedish newspaper lately that showed IKEA's cheapest lightbulbs as one of the less flickery ones in the test. IKEA art.nr 303.887.64. So much for the price to guide you.

Tsubasachan 8y ago
Bought an IKEA led lightbulb for €3 and the packaging says it should last 15000 hours. Not bad really. LED lights are alright. Lots of people think that everything used to be better but my memory is too good to fall for that trap.

TheSpiceIsLife 8y ago

LED flicker could prove harmful or fatal if you work with anything that rotates or reciprocates. The rotating / reciprocating mass may appear stationary at some RPM. Just a reminder to only ever use incandescent or halogen lights around machinery you can touch while in operation: drills, lathes, mills, slotting machines, etc.

handzbagz 8y ago
Just how likely is this to happen though, it would have to be the only light source and be flickering with exactly the same frequency as the machinery is traveling at (which i assume for most devices varies a lot). Not saying it can't happen but it does seem stupidly hard to achieve.
- simcop2387 8y ago
  It doesn't have to be going the exact same speed, a multiple would do the trick too. It can also be dangerous if it's close to the same rate since it can then look like it's going slower even if not stopped.
  - TheSpiceIsLife 8y ago
    Or the rotating / reciprocating object may appear to be rotating / reciprocating slowly in the opposite direction. Even after 20 years in the metal fabrication industry that scenario still spooks me.
- deleted 8y ago
  [deleted]
- icelancer 8y ago
  This is uncommon but not rare. Have you ever seen wheel blur or other artifacting of such? It's very easy to make happen artificially under controlled conditions which means it can't be that hard to happen accidentally. Edited to add: Have you ever heard of a timing light for an engine? This works exactly the way you are describing.

arm 8y ago

Have to mention this¹ big HN thread from 2 months ago with lots of discussion about that exact issue. ―――――― ¹ — https://news.ycombinator.com/item?id=18644590 https://news.ycombinator.com/item?id=18644590

MPSimmons 8y ago

I can spot a Cadillac or GMC vehicle on the road a mile behind it from the flicker of the taillights. It's terrible.

timbit42 8y ago
Why do they flicker? Are they AC powered?
- bradyd 8y ago
  You can dim LEDs by turning them on and off really fast using a process known as pulse width modulation (PWM). Ideally for something like brake lights you would use a constant current driver to control the light level to prevent flickering. I don't know why GM is using PWM, but I'm guessing they just use a cheap control circuit. I really hate their LED tail lights. Just moving your eyes from side to side is enough to easily see the flashing.
  - kurthr 8y ago
    Also, due to leakage for large LEDs they are more efficient at higher current. That means that for a given power, you're better off driving them at a higher current for a shorter duration. You can increase the effective luminance without violating the power spec.
yeutterg 8y ago
Agreed. Most car manufacturers' LEDs flicker (just look at any slow-motion video, such as those on Top Gear or The Grand Tour), but GM's are at a much lower frequency that is visible if the vehicle is in motion, or you are in motion.
- nitrogen 8y ago
  I always wondered if anyone ever tried to encode information into the flicker pattern of LED tail lights. I can think of a lot of uses, good and bad.

14 8y ago

This concerns me. About a year ago I went onto a website and ordered 56 led bulbs for my entire house and thought I got a fairly good deal. They worked seemingly well but my eyes always felt strained when under them. Just took my iphone and can definitely see the flicker with slow motion. And when I look at items as I move my head across the room I feel like I can see it as you say and never really knew what I was experiencing before. As someone who always talks about having sensitive eyes to light I am definitely not happy about this and am now thinking about buying flicker free bulbs. Thanks for sharing.

brachi 8y ago
Next time, a good resource is https://ledstrain.org/ https://ledstrain.org/. I found it here in HN and is quite informative for makign decisions on what to buy.

dingo_bat 8y ago

This is why there's such a price gap between hue bulbs and everything else.

pishpash 8y ago

I have electric heating and in the winter there is no energy benefit at all from LED bulbs. I want my incandescents back. They really feel comfortable in a way I can't explain.

copperx 8y ago
They really do. I placed an incandescent on a floor lamp to use it for reading, and it's now the most pleasant light on my house by far. But it gives me anxiety to leave it on for a long period of time because I know it's a huge waste of energy. The second best are my Phillips SceneSwitches, which I really love but don't come in 100w.

copperx 8y ago

Ah! I'm glad someone found the same thing as I did regarding Phillips bulbs. Here's my old post: https://news.ycombinator.com/item?id=18645237 https://news.ycombinator.com/item?id=18645237

tiff_seattle 8y ago

My Philips Hue bulbs visibly flicker when they are dimmed, but not when they are at full brightness. I never had that problem with the old style bulbs. I wonder if that could be fixed with a firmware update?

yeutterg 8y ago
Theoretically, they could, but I don't think Philips really has a financial incentive to update anything that "already works"

kurthr 8y ago

Have you tried this with incandescent bulbs? They flicker at 120Hz too... since they are P=I^2R and driven directly from 60Hz lines. I don't know the amplitude variation that bothers you, but then I don't mind LED bulbs. Of course it's not the LEDs that do this but the cheap AC-DC conversion bridge rectifier.

mgleason_3 8y ago
Yeah, but because incandescent bulb filament's retains enough heat to continue to glow between peaks, their flickering is almost negligible - especially compared to poorly designed LED and CF bulbs.

mixmastamyk 8y ago

Interesting, I used to be very bothered by computer CRT monitors set at 60hz refresh and bright backgrounds. I'd go into the Windows control panel (most often) and increase it as far as it would go at the given resolution. Through trial and error I found that 72hz was acceptable/ok and 90hz and above was great. Other folks generally didn't notice, but sometimes could if I showed them to look sideways etc. This must explain why I've never knowingly been bothered by 120hz LED flicker, it is below my ability to consciously notice. Curious, I took a look at several bulbs, with the mobile at 240fps trick described elsewhere. A new Feit dimmable, new Ecosmart non, a several year old Ikea, and a no-name CFL. All showed flicker except the CFL. All the LEDs flickered, but the amplitude was larger on the ecosmart. Feit and Ikea had a small amplitude. Perhaps they are putting half the LEDs out of phase to get the smaller amplitude, or they should?

mixmastamyk 8y ago
Small correction, the CFL did have some flicker, just small enough I didn't notice on first look.

voycey 8y ago

Our WeWork has them in the kitchens - I feel like I'm drunk whenever I am in there!

kuon 8y ago

Yes, I also have the flickering issue with some LEDs, and I can confirm that (to my eye) the philips LEDs I bought do not flicker. I also have a few OSRAM LEDs that don't flicker.

0x70dd 8y ago

I noticed the same thing when I was playing the guitar. The constant flickering combined with a vibrating string at a high frequency produces a nice looking effect [1], which can be observed with a naked eye (unlike the one in the video). [1] https://www.youtube.com/watch?v=ttgLyWFINJI https://www.youtube.com/watch?v=ttgLyWFINJI

Cthulhu_ 8y ago

I was in a hotel room a while ago which had some seriously flickering LED lights, just everywhere; moving around you could definitely see it. Wasn't pleasant.

BuildTheRobots 8y ago

I'm surprised no one has mentioned hte rise of flickering LEDs on cars - though I think in this case it's caused by PWM dimming. I mean, it looks absolutely fine as long as the light source and viewer are both static - just a shame vehicles tend to be moving :(

graycrow 8y ago
I don't get why DLR LEDs needs PWM at all. It 100% can be done without, even with smooth light distribution.

consp 8y ago

Cheap brands generally use some form of capacitive dropper scheme. These result in the 120/100Hz flickering but is cheap to produce as very little components are needed (X2 class capacitor, maybe some current limiting resistor(s) and a discharge resistor, bridge rectifier, or even skip the rectifier altogether). They are not to be used with a dimmer. Some info on them [1] The switch-mode power supplies in proper lamps get the stuff done way better and there will be no noticeable flicker. Maybe in the order of several kHz in ripple which you cannot see. Also; cheap off brands (looking at you china) sometimes have caps rated at 250V which is far from the peak mains rate of about 320V (in 220/230V countries). [1] https://www.powerelectronictips.com/whats-stuff-capacitive-power-supplies-leds/ https://www.powerelectronictips.com/whats-stuff-capacitive-p...

apexalpha 8y ago

+1 for Philips bulbs. Lights is something that I used to cheap out on but no more. Not buying Philips bulbs is definitely 'penny wise, pound foolish'. Also, Philips Hue!

moftz 8y ago

I bought some LED string lights for my bedroom because they were cheap. They turned out to be incredibly annoying due to the 60Hz flickering. Staring at them, it wasn't noticeable but the moment you moved your head or moved something quickly you could see the strobe effect. I trashed them and bought some incandescent lights.

TrueGeek 8y ago

I tried this with my office lamps and saw the flickering so I bought the Philips bulbs you linked to. They just arrived and I filmed them but they also show the flickering when filmed on an iPhone in slow-mo mode. Do I need to buy a specific model of Philips bulbs? Or is my Ikea lamp the culprit now? I paid a ton of money for a certified flicker free monitor so I'm very keen on making sure the lamps are flicker free as well.

rincebrain 8y ago

You say "don't have this problem", but given sufficiently unstable mains input, the Philips bulbs too will do this. Source: I just had a problem with a malfunctioning light switch (not even a dimming switch, a plain two-state switch) wherein sometimes it would poorly complete the circuit, and one bulb out of the four on the circuit would start oscillating on and off. (If you removed the one bulb, another would start. If you plugged the first bulb back in, in the original slot or another, it would happen to the first bulb only.)