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Some of these cheap LED bulbs have horrible flicker. For a fun time, record a slow motion video of a cheap bulb on your phone and play it back. Like half the d
by spookthesunset 7y ago
Some of these cheap LED bulbs have horrible flicker. For a fun time, record a slow motion video of a cheap bulb on your phone and play it back. Like half the damn video is black (pretty sure it is because they literally chop out half the AC sine wave with a diode). LED Christmas lights are also really bad.
Then compare it to something like a Phillips hue bulb. The difference between the two is pretty big.
On a side note I sometimes wonder if other animals have a quicker “refresh rate” on their eyes and see nothing but very visible flicker on these bad LED bulbs. I also wonder if some animals could see the raster scan in action on old CRTs...
- all_usernames 7y agoDogs apparently have a visual sample rate of around 75Hz, meaning they wouldn't see much in an old analog TV, but newer HDTVs might look realistic to them. https://thebark.com/content/heres-what-dogs-see-when-they-watch-television https://thebark.com/content/heres-what-dogs-see-when-they-wa...
- berdon 7y agoOur two dogs watch our 4k TV often. And bark at various things, actors, subjects they don't like.
- Topgamer7 7y agoHad a dog that would press her nose right up to an ipad screen and move her face around to follow the squirrel, bird, or dog that interested her. She would get very excited about it. She also watched TV. At one point sitting on hind legs trying to elevate off the bed to be inline with the center of the image.
- bradstewart 7y agoOnly one of my dogs appears to recognize things in the TV. She'll bark at something on screen, and my other dog will run to a window or door trying to figure what he missed. Always wondered why...
- joshspankit 7y agoI’m very suspicious of this 75Hz number. We’ve also heard that 60Hz is the limit of human perception but I think we all know now that we actually perceive higher than that (seeing flicker at 120Hz, blind A/B testing of 240Hz monitors, even perceptual flickering for some people in 1000Hz PWM LEDs). Even if that 75Hz number were derived from deep understanding and measurement of the entire visual pathway, there are variations in perception for people, there most likely are for dogs as well.
- waiquoo 7y ago60Hz is the 'flicker fusion rate', meaning if you were changing the frequency of a flashing, stationary LED, ~60Hz would be the frequency where perception transitions from visibly flickering to apparently continuous. It's a lower threshold for refresh rate in the human eye. When you have complex refreshing images (a 2d computer screen rather than a point-like LED, diverse motion, depth, etc), you are likely to notice flickering (or tearing, jittering, non-smooth motion) if the refresh rate is near this minimum.
- barrkel 7y agoPeople routinely watch movies which refresh at 24Hz and motion is apparently continuous. Perceiving flicker has a higher threshold. I can perceive 60Hz flicker in my peripheral vision easily enough. Other sources online (you can find lots of them but I didn't see an obvious authoritative article) suggest that 16Hz is the flicker fusion rate for motion in humans. Flicker fusion for continuous brightness (CFF) is somewhere around 30Hz per https://www.nature.com/articles/s41598-017-15034-z https://www.nature.com/articles/s41598-017-15034-z and it rises with brightness - this paper is about testing how it changes in different circumstances.
- svachalek 7y agoUnless the camera moves fast and then it looks like a slideshow. Whenever they pan across a landscape it makes me grit my teeth.
- brutt 7y agoYep. See https://www.youtube.com/watch?v=Q-p747h4HKw https://www.youtube.com/watch?v=Q-p747h4HKw for example.
- Someone 7y agohttps://en.wikipedia.org/wiki/Flicker_fusion_threshold https://en.wikipedia.org/wiki/Flicker_fusion_threshold. Classical 50/60Hz lighting looks like a stroboscope to chickens. There is a whole field of research on the effect of light regimes, light color and flicker on poultry farming efficiency. I couldn’t find a scientific link, but see https://agrilight.nl/lichtadvies/pluimvee/?lang=en&-en https://agrilight.nl/lichtadvies/pluimvee/?lang=en&-en
- tasogare 7y agoPhilips bulbs are also at least twenty times more expensive, which is a lot of money for a light bulb.
- codereflection 7y agoTrue, however they are worth the price. I used various brands of LED bulbs for a long time (such as Cree), basically whatever Home Depot was selling. The failure rate was extremely high. In 2017 I switched to Philips LED bulbs, and just last night the first one failed. Overall they are worth the extra up front cost, they'll save you money in the long run.
- spdustin 7y agoI have three weighty Philips bulbs mentioned in the teardown as carriage lights on the exterior of my house. They've been on 24/7 for maybe seven years now.
- Scoundreller 7y agoDon’t underestimate the thermodynamics of a slight breeze vs. Passive dissipation alone.
- hocuspocus 7y agoYou don't need to buy Hue... Their 8W 800lm bulbs are €4 a piece in Europe, and a lot less in bulk. So 4x more expensive at worst. Philips' discount brand (Attralux) is even cheaper, I recently bought more of these 8W 800lm for less than €1 a piece. For now I cannot tell the difference.
- altcognito 7y agoAt five times the cost, they had better be higher quality bulbs. $13 is pretty steep for a single bulb.
- derefr 7y agoIt’s not like these bulbs are flickering in a way you can perceive just by slowing it down by 2/3/4x. They’re flickering at 10000+ Hz. The reason cameras perceive the flicker is that they take discrete samples, with an (electronic or optical) shutter in between. This creates a beat frequency with things that also flicker, in effect “tuning into” a HF flicker and “lowering it” into the visible range, the same way a superheterodyne radio tunes into a HF carrier wave and brings it down into the audible range.
- Robotbeat 7y agoFilament LED bulbs usually flicker at 120Hz (with high duty cycle) and Christmas LEDs at 60Hz (with a short duty cycle). Other LEDs are, indeed, high frequency like you describe and are perceptually effectively constant.
- vidanay 7y agoThe filament in a filament bulb doesn't fully cool down when the voltage crosses to zero, so that smooths them out a lot. Sorry...I just noticed you are talking about filament LED and not old fashioned analog filament bulbs.
- smoyer 7y agoYep ... it's the digital (meaning on-off) version of the slow moving line you see if you point your camera at a TV (or computer) screen - the speed that it happens at is the sum and the difference of the two frequencies (and perhaps at the sum/differences of their harmonics). In the CATV industry, we used to send 110 analog channels across roughly 800MHz of spectrum (54MHz to 860MHz). Other than background and ingress noise, a major source of noise (effectively) was distortion - non-linearities in the amplifiers that kept the signal at a reasonable level. Composite Second Order (CSO) and Composite Triple Beat (CTB) distortions were two values that equipment transporting these signals would generally call out - they are analogous to the summing and differencing of two signals and three signals (respectively) as described above for the lightbulb, but imagine doing that with 110 different frequencies simultaneously.
- spookthesunset 7y ago
- tyingq 7y agoI don't know about the bulbs, but commercial LED drivers from companies like Meanwell typically let you select a range between 100Hz and 1000Hz for the PWM frequency.
- Robotbeat 7y agoThe filament bulbs are almost all like this. Not too bad if they're using an H-bridge (120Hz with high-ish duty cycle), but Christmas LEDs I think might use no separate diodes at all, just relying on their own diode-ness. That means they're 60Hz with a less-than-50% duty cycle. Filament LED bulbs (the ones that look almost exactly like clear incandescent bulbs with a visible filament when turned on) do this because they have to fit their electronics in the tiny metal base. Room enough for some diodes (and maybe a capacitor), but usually not a full set of high frequency switching electronics like in most other LED bulbs (although I've seen some filament bulb tear downs that might show more advanced electronics). But again, doesn't bother me due to their high duty cycle and relatively okay refresh rate. (At least, this is all my impression. Please correct me.)
- Tepix 7y agoAre there any statistics how many people perceive this flicker? I see them complain in online forums but I'm not sure if it's just a very loud small minority. What does it take to make them not flicker? I.e. how much of a cost increase is required?
- uxp 7y agoBased upon this article were the retail costs of a cheap flickering LED bulb is approaching the single dollar mark, the cost increase to use a proper AC/DC converter could be orders of magnitude more expensive (at a rough minimum). Honestly it's starting to feel like a most cost effective long term solution is to build homes with a master AD/DC converter (or several depending on sq/ft) and simply wire 12v outlets and light fixtures. The energy savings of swapping all incandescents or compact florescence bulbs with cheap LEDs with cheaper power converters is starting to scare me knowing just how shoddy and fire prone some of these power converters can be.
- BlueTemplar 7y agoI expect USB-C outlets to become common in new homes...
- macNchz 7y agoYes I find these cheap LED bulbs nearly intolerable-the flicker is especially noticeable because they transition so quickly from fully illuminated to fully dark. I’ve always perceived a slight flicker from fluorescent lights but because the phosphors smooth it into more of a fade in and out it’s much less distracting. I definitely think people perceive these things differently...I recently stayed in a hotel room lit entirely by these cheap LED bulbs and it was the first thing I noticed from walking in. It really bothered me that every light fixture strobed as I moved my eyes, but my girlfriend barely noticed it and only after I pointed it out. The OLED displays in current smartphones also exhibit a visible strobe effect at lower brightness settings. I figured I’d get used to it but ended up returning my iPhone 11 pro after a week because it was driving me nuts. I’ve met a few people who perceive it as well but most seemed to have no idea what I was talking about.
- gumby 7y ago> On a side note I sometimes wonder if other animals have a quicker “refresh rate” on their eyes. Indeed, to the housefly, an incandescent-bulb-lit house slowly pulses from light to dark, so probably too with cheap line voltage choppers.
- SamBam 7y ago> an incandescent-bulb-lit house slowly pulses from light to dark This sounds amazing to me, but also confusing. My understanding is that an incandescent bulb works entirely by heating up the filament. There should be no way that the filament is cooling down and heating up in anywhere close to the rate that it would require to get some kind of wagon-wheel effect, which is what it sounds like you're describing.
- pwg 7y agoIgnoring 'complex power' concerns, the AC voltage driving a tungsten filament bulb is a sine wave at line frequency (60hz for the US). Because it is a sine wave, and because the tungsten filament is a resistor, the current through that resistor rises and falls in sync. with the AC sine wave. The current will be zero at the zero volt crossing point of the wave, and maximum at the peaks of the sinewave. The varying current through the tungsten will result in a varying power consumption (varying at a 60hz rate). The varying power consumption will result in a small amount of varying temperature on the filament. Now, the filament does not cool down instantly, so the result is its temperature will vary by a few degrees, but likely not enough to ever be perceptible to human eyes. But with a sensitive enough (and fast reacting enough) temperature probe, one could likely measure the temperature rise/fall of the filament that is synchronized with the line frequency.
- SamBam 7y agoRight, the wave filter effect caused by the thermal mass of the filament was my point. I'm not sure you've shown that this would be visible to a housefly as a "slow pulse from light to dark," as the post I was replying to claimed. First of all, you said the power consumption will vary at a 60hz rate, but it seems to me it will vary at a 120hz rate, since the current will be at its max magnitude twice per cycle (as you say in the first paragraph). But more to the point, I don't know whether the temperature/lumens will decrease enough in 1/120th of a second to be visible to houseflies or anything else. Trying to research the answer, I found this physics lab worksheet [1] from Pasco (the makers of sensors), for a high school lab measuring the output frequency of incandescent bulbs vs fluorescent bulbs, but without doing the lab I don't know the results. 1. http://phylab.yonsei.ac.kr/exp_ref/pasco/P54_BULB.pdf http://phylab.yonsei.ac.kr/exp_ref/pasco/P54_BULB.pdf
- tootie 7y agoMy cheaper LEDs also seem to get destroyed by a dimmer much quicker than better ones. Not sure if that's related.
- Dylan16807 7y agoProbably not directly related. Dimmers cause voltage spikes, and cheaper models are less equipped to handle that.
- hinkley 7y agoI used to be able to detect the flicker by eye, or sometimes by waving my hand. But they pack so many into the demo display at the store that when I moved I had to use the slomo feature of my phone to pick the right LEDs.
- LinuxBender 7y agoI can tell when I am around these bulbs. It is the same with fluorescent lights for me. They make me (more) grumpy. The more expensive LED lights have full wave bridge rectifiers and capacitors with no flicker. I've considered just building my own for my next home.
- tomatocracy 7y agoSome LED lights/bulbs also incorporate phosphorescent materials and use UV LEDs to stimulate the phosphor which helps too. This is also one of the ways better colour reproduction can be achieved. This comes at a slight efficiency cost though, I think.
- extrapickles 7y agoMost LED lights use the UV+phosphor technique as its cheaper than doing RGB (If the LED is yellowish when switched off, its using this technique). The best flicker-free lights are ones that have low ripple constant current power supplies (somewhat expensive). LED lamps intended for use around rotating machinery used to all be this way until someone figured out that if the PWM frequency was wildly unstable it would prevent the problems with strobe lights around spinning things at a fraction of the cost.
- scarejunba 7y agoThat is just the stroboscopic effect. It’s an artifact of your measuring tool. I’m not saying that your lights aren’t flickering but your tool is introducing a lot to this system and so you can’t use it as evidence.
- gibolt 7y agoPigeons have a "refresh rate" of around 100 frames per second. It is believed that a bunch of smaller animals and even insects have similar or faster visual processing time, though I'm not aware of specific numbers.
- ksec 7y agoI have been thinking about this for years! I think we need a new marketing term along with a independent organisation to push for a new LED Standards. Let say it is called CLED, And it requires the following features / spec before it could be called CLED. From PWM, Colour Correctness, Energy Efficiency, heat etc. The different between a low price light bulb and higher priced is relatively minimal , the difference in LEDs is massive. To be point they should not even be allowed into the market in the first place.
- tomatocracy 7y agoBrand (and in some cases sub brand) is a reasonably good proxy for this already though. Philips bulbs for example tend to be very good.
- 0xff00ffee 7y agoFunny you mention animals. I often wonder if home environments have become screaming dens of high-frequency noise for dogs and cats. I know that flourescents tend to osciallate around 40kHz, and I definitely have an LED bulb that whines for some reason. Not to mention cheap laptop power supplies that also whine over time. Are all these cheap SMPS driving our pets insane? (or just annoying them? or neither?) I wonder if I could rent some super-high-quality mic from a local sound reinforcement studio and look at a 20-60kHz FFT ... or do fancy mics not really go beyond human hearing?
- dspig 7y agoHigh quality recording mics and even mics designed for acoustic measurements usually (and deliberately) only go up to 20-40 kHz though roll off more gently than human hearing. Usually there is a mechanical resonance that's tuned to get a flat frequency response up to a point rather than a wider but rolling off response. A few specialist mics get up to 100 kHz, or some sort of laser vibration measurement...
- Junk_Collector 7y agoThis is actually a pretty big deal if you work with high speed or rotating machines. Using an high flicker LED bulb over your lathe (for instance) can cause it to appear static when it is in fact running due to visual aliasing. There are lines of flicker free LED bulbs for industrial spaces for this reason.
- timmytokyo 7y agoHas anyone done a comparison of flicker in available LED bulb brands?
- brewtide 7y agoCan you recommend the optimal bulb between price and "flicker free smartphone slow mo" ? Just white. We run whatever cheap bulbs in my house at the moment, but also tend to do to a lot of "slow mo" videos and it kills me every time. I'd prefer NOT to spend $15+ a bulb for crazy high end but would be more fine with say, $5+ a bulb