GregAtkinson Thanks for the suggestion of light bulbs! I'll have to try those.

When detecting differences in the flicker of different color subpixels, for Nightshift, I measured the flicker of the different subpixels (using the microscope and slow-motion video) on a completely white (or sometimes gray) screen without Nightshift and then using the same white (or gray) screen, but with Nightshift turned on at its warmest. It's super labor-intensive to do this using the Photoshop histogram/luminosity function, but I was glad I did. Before doing this test, I could feel that Nightshift was doing something that badly hurt me, but before this test, I didn't have good evidence for why. It's dramatic how much more the green and especially blue subpixels are fligckering than the red supixels during Nightshift.

I could also detect differences in the flicker of different color subpixels (without Nightshift) using other colors on the screen. To find dramatic examples to measure with the microscope (since microscope/video measurement Photoshop analysis so labor intensive and triggering of symptoms for me), first I measured flicker with a flicker meter of different colors when only a single R, G, or B value was nonzero, at many settings. Then I chose to make 2 of the R, G, or B values nonzero, choosing combinations of values that on their own gave different flicker meter readings. Then when I recorded slow-motion microscope videos, i could see and quantify differences in luminosity of differently colored subpixels as they flickered. I could also put camera color filters between the flicker meter and the screen to get readings for different colors (Tiffen Red25, Blue47, and Green58 filters were the most useful for me). However, the microscope slow-motion video measurements tended to show color-to-color flicker best because I could measure individual subpixels and didn't have the interference between differently-phased flicker patterns that obscures readings with the flicker meter. Different screens had different colors with the most dramatic color-to-color flicker. On the screen I use most, i can mostly limit the colors that are used. I immediately feel pain/pressure in my head if I have even a small part of the screen displaying something with high color-to-color flicker.

I'll be interested to hear what you find out with your method!

      Yes, I can use the Waveform Centric Home A19 bulbs when they're new, but they start to flicker badly and cause brain injury for me as they age. You can see my measurement of the flicker of these bulbs over time here:
      https://www.flickersense.org/testing-leds-and-screens

      I stopped using Waveform Centric Home bulbs at home and switched back to incandescents with low flicker, but we still use Waveform bulbs at a family member's home. I just test their flicker periodically with a meter now. I'm glad they're still working for you!

      We also tried some of their commercial lights at my workplace, but they flickered and injured my brain even when they were new:
      https://www.flickersense.org/testing-leds-and-screens-before-2023

          jen

          Thank you for sharing and for that wealth of information that is your website. Not sure if this is some kind of bias, but I recently been testing some old incandescents and they seem more comfortable than the waveform products I have (a19 bulbs and their led strips). The led strips are 12 volt battery powered.

          For pixel flicker recordings, I am considering upgrading from my samsung 240 fps phone camera to a sony a7s III (also 240 fps capable) or some similar camera with very good sensor noise performance to reduce the impact of video noise on the analysis. I also feel eyestrain just from doing measurements with the samsung phone itself as it uses PWM OLED screen.

            smilem I wonder what store reps said when you showed up with ghostbusters kind of gear, and "I want to test all your phones and screens in the store !" ???

            We had a nerd fest! It was pretty cool. About five of them stopped by one at a time and asked (in a nice way) what I was doing so I showed them the non-flicker of my own laptop and then the flicker of the monitor I happened to be testing at the time. A couple of them even asked to see me test a particular monitor. Even a couple customers got into the mix.

            This was at Micro Center, which is kind of a nerdy place. (I use Nerd as a compliment, btw).

              Please can you clarify you measuring methodology?

              At what distance you measure from screen, what C mount lens you have attached that makes ZOOM possible?

              The sensor PDA100A2 is uber expensive "at what it does". The Lupin old model (that cost 100Eur) without white diffuser measures really well up to 3000Hz sampling at 6000Hz and even outputs to android with 3 band peaks identified.

                smilem I hold the device up directly to the screen. The device's housing blocks out all external light. The zoom/gain is a feature of the device. There are 8 gain settings that go from 0x all the way up to 3,000x.

                I've had the old Lupin for quite a few years. I did not find it useful for testing screens. I found the DIY light detector described elsewhere on this forum to be quite a bit better. The Thorlabs PDA100A2 was $450, but worth every penny to me.

                  "I've had the old Lupin for quite a few years. I did not find it useful for testing screens. I found the DIY light detector described elsewhere on this forum to be quite a bit better."

                  The Lupin can measure up to 3Khz, why you found it not good?

                  Why not use Thorlabs DET36A2 biased photodetector 124USD ? 11Mhz vs. 25Mhz for cheaper version is faster. Why not use OSRAM BPW34S PIN (cost 1.7Eur) photodiode up o 400Khz it works the same as Thorlabs DET36A2.

                    smilem

                    Acer V3-771G (2013) is flicker.

                    MVA panel / PWM 200Hz.

                    Checked through Radex Lupin.

                      smilem The Lupin can measure up to 3Khz, why you found it not good?

                      Two things I didn't like about the Lupin. First, I like to see the actual graph, not just a flicker percentage. It's not just how much the light source is flickering, but how abrupt the light is flickering that affects me. For instance, incandescent bulbs flicker with 120hz, but they don't bother me. Second, maybe it was the 3Khz limit, but it wasn't reliable in detecting PWM.

                      smilem Why not use Thorlabs DET36A2 biased photodetector 124USD ? 11Mhz vs. 25Mhz for cheaper version is faster. Why not use OSRAM BPW34S PIN (cost 1.7Eur) photodiode up o 400Khz it works the same as Thorlabs DET36A2.

                      The big feature with the PDA100A2 is the switchable gain/zoom. For nearly all the graphs on this page, I'm using 100x zoom.

                      There may be cheaper alternatives. For instance, I know there's a 10x/100x gain amplifier on eBay for about $70. So maybe you could hook that up to the BPW34S and get good results. (In fact I bought it a few weeks ago, before I got the PDA100A2, and just never got around to using it.)

                          FYI, I've been using the new monitor daily for the past three days for 4+ hours/day and it's great. No headaches. (I'm confident that I could put in full 8 or 12 hour days without headaches, but the nature of my life right now is that I'm not at my desk all day.)

                          Later this week I'll head to Micro Center and buy as many as I can (they say they have 12 in stock), test them for flicker, and let you know what I find. They are still on sale for $130 plus tax.

                          6 days later

                          And of course by the time I got to Micro Center on Friday they were out of stock. So I'll check back daily until they're back in stock. (One of the staff said they should get them this week.)

                          Also, I counted the number of monitors on display and they actually have about 100. Some may be duplicates of the same model, but my point is that it's not easy to find a monitor with no flicker. Only 3 out of those 100 (one 27" and two 24") were flicker free/virtually no flicker.

                          qb74 You could also use Rtings' tests for monitor flicker, which is pretty reliable

                          My hypothesis is that I'm sensitive to very small amounts of flicker (too small to show up on the Rtings tests). I have a number of devices that are supposedly flicker-free that give me headaches.

                          • jen replied to this.

                              GregAtkinson qb74 I'm also sensitive to very low amounts of flicker. The screen flicker can be virtually nonexistent when measured grossly with a flicker meter. For me it seems that for screens lacking dramatic backlight flicker, my symptoms are worse with higher flicker of the individual subpixels that can be quite high and visible with a microscope and slow-motion video, but masked when measured collectively with a flicker meter so that it's virtually undetectable. And my symptoms are even worse when the pattern of subpixel flicker differs for the red, green, and blue groups of subpixels. I've also found that the pattern and magnitude of subpixel flicker varies widely for different colors and on different screens. Testing data and methodology here. Unfortunately, methods used currently on rtings or notebookcheck that only use some form of flicker meter/oscilloscope to grossly measure flicker of a relatively large screen area identify dramatic backlight flicker, but aren't able to detect what's happening with the subpixels and also generally aren't able to detect any color-to-color flicker. They should also be checking flicker when different colors are displayed. It's also true that even if only backlight flicker is considered, even extremely low flicker can cause brain injury for me, since some LED lights with less than 0.1% flicker cause injury for me.

                                    jen I've also found that the pattern and magnitude of subpixel flicker varies widely for different colors

                                    I've noticed with pixel inversion that the light colors (light green, light red, light blue and combinations of those colors) often flicker more than darker colors or fully bright colors. I'm thinking it's probably technologically easier to be fully on or fully off, but the colors in the middle have more variation when switching polarity from positive to negative.

                                      I bought 10 of the LG 27MQ450-B monitors today. I tested one today and it looks great.

                                      White at 100x zoom (brightness 100%, contrast 40%)

                                      #D0D0D0 at 100x zoom (brightness 100%, contrast 40%)

                                      dev