PuffyCloud It sounds like you measured the "FfT" bulbs you tried. Did you measure any frequencies, and what exactly do you mean by "they go dark"? Like, really no light anymore? This might be very important, please reply.

I just measured my headache bulb which I still own with my oscilloscope setup. It is the "GreenAndCo TM-A19-6W-E27-W". I did not find frequencies other than 50 Hz and 100 Hz apart from very small fluctuations around 60 kHz. The latter are so small they only truly appear in the spectrum analysis (and only in AC mode). And the visible 100 Hz ripple appears to be very minor, too. At most 5 mV out of 600 mV total amplitude. That is well below 1 % difference. Can such small differences really cause headaches?

23 days later

These Chinese Corn LED bulbs do flicker (pencil test), but they do not cause any eye strain for me.

Their parameters:
Voltage: 220V
LED type: SMD 5050 (square).
Color: warm white.
Image:

The bulbs which DO CAUSE eye strain to me immediately:

Brand: Philips
Voltage: 220V
MPN: 9290011717A (9W, warm white)
MPN: 9290011718A (6W, warm white)

    a month later

    So I took my Fauser LiFli flicker detection device and went to a local IKEA store to measure the currently available bulbs in their lighting section. The vast majority of their lamps and bulbs flicker. However, some of them showed no sign of flicker on the device, which means the flicker must be below 1.5%*. So I bought those bulbs and took them home, measuring them with my oscilloscope setup. I tried to carefully measure even slightest fluctuations. Here are the results:

    • IKEA LUNNOM LED 600lm 5.5W 2200K E27 [703.545.64]: ~30% 100 Hz flicker that goes down to steady 0.41% 100 Hz flicker within ~7 seconds, no measurable high frequencies
    • IKEA LUNNOM LED 100lm 1W 2200K E27 [003.821.84]: borderline measurable 0.03% 50/100 Hz flicker (the 50 Hz part may be photodiode circuit noise), no measurable high frequencies
    • IKEA LEDARE LED 600lm 7W 2700K E27 [903.887.75]: 1.24% 100 Hz flicker, decreasing over time down to 0.29% 100 Hz flicker after some minutes, 0.33% 80-100 (varying) kHz DC ripple
    • IKEA LEDARE LED LED1719R6 400lm 5.3W 2700K E14 [503.658.27]: instant 0.18% 100 Hz flicker, no measurable high frequencies (total brightness decreases a little over time)
    • IKEA LUNNOM LED LED1641C2 200lm 2W 2200K E14 [403.545.32]: instant 0.06% 100 Hz flicker, no measurable high frequencies

    Those bulbs have E14 and E27 sockets. They are compatible with 50/60 Hz 220/240V~. They seem to be available in other EU countries' IKEA stores, too. Maybe for those countries who have a different power network, they share the same flicker characteristics world-wide.

    I must see over time how those bulbs work for me. What's great so far is they don't make me feel sick after some minutes like other LED bulbs did. Plus currently I'm under the impression that truly flicker-free LEDs don't exist as long as they are powered by AC.

    * (I adjusted the device to show flicker percentage as (A-B)/A, where "A-B" is the difference between highest and lowest amplitude, and A is highest amplitude. My oscilloscope results are also calculated with this method.)

    Edit: Almost forgot, I took a photo of a GU10 LED that I didn't buy but was "flicker-free", too:

    Those bulbs that I bought, they still hurt. I can't use them a whole evening without pretty severe eye strain. As it is hard to believe that 0.03% of flicker would cause anyone any trouble, maybe the flicker theory has reached a dead end. My incandescents, which flicker at 20-35% are much more comfortable.

    a month later

    In my backyard there are some street lights for everyone to use when it's dark, so people find their garage and car. I found whenever they used the lights, which turn off automatically after 5 minutes, I O eye strain that persist for 1 hour+. The light that was coming into my room was very subtle. However, I made sure to buy light-blocking roller blinds and curtains to minimize the light.

    Edit: A long text got destroyed because my phone's battery died. And I typed it on the phone. I'm not typing it again. Short form: suddenly eye strain in a dark room with everything closed, windows behind me, looking at the bright (known-good) phone screen. I look outside and realize someone has turned on the streetlights. A small reflection on the wall and ceiling caused the eyestrain. The lights flicker at 100 Hz. The reflections are very faint plus not remotely visible when you look at a bright screen.
    I'm telling you this to raise awareness that even slightest changes could cause eyestrain. FRC, temporal dithering, the LED bulbs I tried, their flicker is extremely low. Yet they cause trouble. I blocked blue light on my bulbs and verified it was truly blocked with a spectrometer. Blue light is not their issue. Only the flicker remains. And even very low percentages of flicker seem to cause eye strain.

    2 months later

    Solf that bulb flickers at a rate of 220/2 = 110 times per second. I assume it's 220v AC current ur using. Most phones and screens if I remember correctly flicker anywhere been 800 to the thousands per second with PWM or oled.

    • JTL replied to this.

      Doesn't an regular old-fashion lightbulb flicker because of AC current? Yet most people aren't bothered by them here?

        ryans Yes, they flicker because the power network in our countries is constantly switching the current direction and no attempt is made in either lamps or bulbs to convert AC into DC.

        I have trouble with some incandescents. It is not caused by the bulb per se. Must have to do either with the lamp electrics or how the light reaches the eye. My bathroom light is always good, my living room light hurts a little over time, and the very bad IKEA "Holmö" lamp that I have bought a while ago gives PWM symptoms immediately, even when the light source is out of sight. Couldn't measure any differences yet on oscilloscopes, but it's hard to do precision measurement on ceiling lamps.

        ryans should only glow 60 times a minute. Or 50 if you use Pal. I heard the biggest problem people were having with these is really cheaply made rough service bulbs. I know two people this was causing eye strain to.

        • KM replied to this.

          KM

          KM I never knew that. No incandescent has ever bothered my eyes. I don't know how I did function otherwise.

          KM I think this raises a very interesting question. Why is 100x a second flicker in a light bulb fine, but, 220 Hz OLED flicker is not?

            ryans I don't know the answer. One could argue that the 240 Hz OLED PWM has a larger flicker percentage (the difference in amplitudes) or in general a faster rise/fall time. But ultimately, no solid theory.

              KM

              ryans You are not looking at the light bulb directly.

              Also what hurts you in the oled might not be the pwm, but the dithering of the OS.

                4 months later
                9 days later

                Yesterday I replaced a dead incandescent bulb in my kitchen with an LED bulb that doesn't flicker to the point where only more sophisticated measurements reveal 0.06% 100 Hz flicker without any warm-up phase (some other bulbs flicker terribly until they've warmed up). The light intensity is very low at 200 lm. The light itself is very orange, much warmer than any incandescents. As the orange color already indicates, a handheld spectrometer shows only negligible amounts of blue light. After some minutes, the light begins to stress my eyes nonetheless. I woke up with burning eyes today. It remains a mystery why LED bulbs are not usable for me. The E14 small version incandescent bulbs had strong 40% 100 Hz sine wave flicker and seemingly more blue light, but were usable.

                And my good old bathroom lamp "IKEA PULT" died, so I replaced it with the latest PULT version and the regular incandescent bulb inside it suddenly triggers symptoms. I never knew why the old lamp was so comfortable to look at and I don't know why the new version triggers eye strain. I looked at the electronics and found there most probably are no electronics at all in both lamps. Instead, the ceiling cables go directly to the bulb socket. A difference is the new version has a frosted glass cover while the old one had a milky one. The measurable flicker hasn't changed, still 25% 100 Hz sine waves as usual (60 W bulb).

                  KM The light itself is very orange, much warmer than any incandescents. As the orange color already indicates, a handheld spectrometer shows only negligible amounts of blue light.

                  Sounds like the lights in my office, although LED. So what now, are we sensitive to the orange color?

                  What about the PULT? Is it incandescent and still hurts? What about the color?

                  • KM replied to this.

                    AGI PULT is just a ceiling lamp with a regular bulb socket that you can put any bulb in, be it incandescent, energy-saving, or LED. It has a glass cover, but the color is not changed by much.
                    https://m2.ikea.com/us/en/p/pult-ceiling-lamp-steel-10193300/

                    I'm sensitive to all LED bulbs I've seen so far regardless of color (orange up to bluish). Some are extremely aggressive and some less. But the "blue light" and "flicker" theories are maybe not enough to explain problems with orange and (almost) flicker-free bulbs.

                      dev