GregAtkinson I ordered one. I appreciate all your effort on this, and I’ll plan to report back with results.

Possible reservations I considered were, 1) usually I prefer 1080p screens at around 23”-24” (but, perhaps larger pixels can be easier for the eyes to focus on, so worth a shot), and 2) I think my personal issues are more related to modern LED backlights (with the red hue, in almost all the screens I tried), as well as software/driver causes, versus hardware-related flickering. Still, your testing seems promising, and I am happy to explore this further.

    One bit of good news is that these monitors are very consistent in terms of flicker (the serial numbers are nearly sequential). Here's a screen shot of the monitor I'll be sending to @macsforme. It's 30x zoom on a white background, which is pretty much identical to the other monitor I tested from this batch.

    And here's the worst color I could find (#D0D0D0)

    Is there a higher frequency, too? The lines look kinda jagged. Did you measure that frequency? It may become more pronounced if using a time unit lower than the depicted 10 ms per div.

      KM Good question. The other frequency is the backlight, I assume. This is at 100x zoom. You can see two lower frequencies. One every 25 us (40khz) and one every 3 us (330khz)

        Have you heard about hybrid PWM? Dell U2713H (2012) can use two types of flickering at the same time. Up to 50% of the brightness flickers with a frequency of 1000Hz (every 25ms). At brightness 20-50% hybrid (double) PWM. Second flicker at 11500Hz frequency (every 285ms). Dell U3219Q (2018) also flickers every 250/5ms. One flicker is low-frequency, the second high-frequency. At the same time, monitors are declared as Flicker Free. The information was taken from the TFT Central and Prad.de sites

        GregAtkinson I read a couple places that this monitor supports 167 colors. I assume that means 167 out of a possible 256.

        Whoops… I just realized that 167 means 16.7 million… (And according to Display Specifications, it's 6 bits + FRC.)

          I've been thinking about what a few people have been saying about refresh rates, temporal dithering/FRC, screen size, etc.

          I had tested about 100 monitors and I took screen shots of the ones that had OK flicker. There ended up being 19 monitors with OK flicker. In other words, if you're willing to put up with a bit more flicker for a faster refresh rate or a true 8-bit panel, then this list could be useful.

          ManufacturerModel #RefreshColor depthResolutionScreen sizeResponse time
          SamsungU28R5560Hz8-bit + FRC3840 x 2160284 ms
          HPM27h FHD75Hz6 bit+ FRC1920 x 1080275 ms
          LG27UP60060Hz8-bit + FRC3840 x 2160275 ms
          SamsungS27BG40240Hz8-bit1920 x 1080271 ms
          HPM27h75Hz6 bit+ FRC1920 x 1080275 ms
          HPM24h75Hz6 bit+ FRC1920 x 1080245 ms
          Dells2422hz75Hz6 bit+ FRC1920 x 1080244 ms
          LG24mq450-B75Hz6 bit+ FRC1920 x 1080245 ms
          LG27mq450-B75Hz6 bit+ FRC1920 x 1080275 ms
          LG29wp50s75Hz6 bit+ FRC2560 x 1080295 ms
          LG32up83a60Hz8-bit + FRC3840 x 2160325 ms
          Philips45b1u6900ch75Hz8-Bit5120 x 144045 (curved)4 ms
          MSIg271cp165Hz8-Bit1920 x 1080271 ms
          MSIg321cu144Hz8-bit + FRC3840 x 216032 (curved)4 ms
          Lenovog32qc-30165Hz8-Bit2560 x 1440321 ms
          Lenovoq27h-1075Hz8-Bit2560 x 1440274 ms
          AcerEI322QUR sbmiipphx165Hz8-Bit2560 x 1440321 ms
          AOCCq32g3su165Hz8-Bit2560 x 1440321 ms
          DellSE2422H75Hz6 bit+ FRC1920 x 1080245 ms

          qb74 You could also use Rtings' tests for monitor flicker, which is pretty reliable
          https://www.rtings.com/monitor/tests/motion/image-flicker

          Now that I look closer at the site, I shouldn't have dismissed it so quickly. If you really look at the waveform closely, you can see whether it flickers or not. Here's a good example that I took from their site that doesn't seem to flicker:

          https://www.rtings.com/monitor/reviews/asus/rog-strix-xg27aq

          I kinda got thrown off by the fact that nearly all of their monitors receive a rating of 10 for flicker (10 being the best). But if you ignore their numerical rating and look very closely for a perfectly flat, thin waveform, you could probably find a flicker-free monitor that way.

          • qb74 replied to this.

              You bought an LG 27GL650F-B (8bit) monitor, what's next?

              Want to know how "response time" affects pixel flickering?

              The backlight will flicker if you turn on MBR (black frame insertion)

              I bought a true 8-bit monitor just to see if I could tell a difference between that and 6-bits+FRC. It a fairly inexpensive monitor ($228). It's a Lenovo Q27h-10. 27", true 8-bit (according to https://www.displayspecifications.com/en/model/01a62201). 75hz max frequency.

              The flicker is about 1.4% using the formula (max-min)/max. It's in the top 10 (out of about 100 monitors tested) in terms of low flicker.

              This screen shot is 100x zoom, 100% brightness and 30% contrast.

              I haven't used it yet (I have a bit of a headache today), but I'll report back in the next week or so.

              GregAtkinson Another thing Rtings is good at is to look for response times charts. Certain trainsitions / colors may flicker as well.

              Such as this VA panel during a rise transition (from darker to lighter shade)

              This sawtooth wave u can see in the scope is very likely related to the scanline logic, a brightness dip happening every refresh cycle due to it (180hz = 5.5ms)
              This is measured with a 12bit scope + thorlabs photodiode.

              I wouldn't be surprised if this is the issue you're experiencing on the monitors you've tested.

                  qb74 I wouldn't be surprised if this is the issue you're experiencing on the monitors you've tested.

                  Yeah, I've seen a lot of waveforms like that. I zoom in 100x so the waveforms are a lot easier to see. That particular monitor would likely not work for me due to the noisy waveform and sawtooth pattern. Eyeballing it, it looks like the flicker is about 5% or so.

                    I received the LG 27MQ450-B from @GregAtkinson last weekend, and I set it up as my main monitor at work to give it a thorough test. Around the same time I also received the Opple Light Master 4 I had ordered, which I know has limited capabilities, but I thought it would at least provide an empirical measurement along with my subjective perceptions.

                    Leaving the display settings as they came (Brightness=100, Contrast=40), my very first impression was that the picture appeared somewhat unstable. I had a slight perception of the picture moving or flickering. I took a few readings of a white background with the Light Master, and all readings were something like this (I calculate 12.6% flicker using (max-min)/max):

                    Imgur

                    I ultimately reset the brightness and contrast settings to their defaults (I believe ~75 for both), and the picture looked brighter and more stable, although still not as stable as my old Dell monitor from 2013. I initially thought this might be usable once I got accustomed to it. I took another Light Master reading of a white background, and got this (I calculate 7% flicker using (max-min)/max):

                    Imgur

                    I then tried reading emails on the screen for an hour or so (my typical use pattern). Unfortunately, I got the symptoms I get with most modern displays: focus problems, blinking constantly, a feeling like a flashlight is shining in my eyes, lack of comprehension, etc. I forced myself to use it for a few days, and perhaps adapted to it slightly but not significantly.

                    I am open to thoughts on this, because this sounds contradictory to GregAtkinson's testing indicating very low flicker. My initial thought was that the AC power in my office may not be very clean, or that there could have been a GPU output issue (however, none of these changed from my old setup, which was perfectly comfortable). I was connected via DisplayPort, just like previously (well, previously it was a DisplayPort to DVI adapter), so I wonder if I should try a different cable or try connecting via HDMI. I also am a novice user of the Light Master device, but the measurements do seem to correspond to my real-world discomfort.

                    For reference, this was a Light Master reading of my old Dell monitor from 2013, which I found perfectly comfortable (the PWM is quite evident, but I can use this all day long):

                    Imgur

                      macsforme I took a few readings of a white background with the Light Master, and all readings were something like this (I calculate 12.6% flicker using (max-min)/max):

                      You and I get pretty similar results with the Opple, FWIW. Here's what I got with my monitor. I think I'd probably turned the brightness down to 50%, hence the lower absolute values. But the percentage flicker is roughly the same.

                          I think the bigger issue is FRC, maybe that's what is causing those symptoms.

                          dev