u/BearNecessary4141

TM-39-25 is a document from the Illuminating Engineering Society that puts forth a classification system that seeks to reduce human responses to flicker. I often call the classification system itself "TM-39-25".

The system utilizes three different flicker effect visibility metrics, Mp, SVM, and PAVM. These metrics are scores computed from the flicker waveform that seek to predict the likelihood of a "temporal light artifact". I go over each metric in detail in the video, but here's a summary table:

https://preview.redd.it/wcv2st4dl8kh1.png?width=2720&format=png&auto=webp&s=959251de6d086b0e7e14ac6f2db3e2f29c9538ed

Simply put, a temporal light artifact is a visual disturbance of some kind due to flicker. TM-39-25 classifies light sources based on all three metrics simultaneously. I see this classification system as a vastly improved (but not perfect) replacement for IEEE-1789 classification, which are the frequently posted here as part of the results the Opple Light Master produces. Here's how the metrics scores map to the classifications:

https://preview.redd.it/eu77sdtkl8kh1.png?width=1505&format=png&auto=webp&s=bdaab419feb5c6a00f6c45dcbbc1bf5b39487d0b

I think this standard can be used as a replacement for the IEEE-1789 classification. The three metrics or "scores" it uses provide much more useful information and were created based on the results of experimental studies.

I have built this system into the flicker meter I'm working on (TLM-110), and used it to measure a variety of bulbs:

https://preview.redd.it/k6h1yilfk8kh1.png?width=2300&format=png&auto=webp&s=4bc5c3624bc7fd71a4c7f82ab347d5ebf3180e51

You can see there's a wide range of classifications in the bulbs I tested, as well as a large spread in the scores. The bulbs that are "Not Recommended" are unbearable to me, while the bulbs that are "Better" are much more tolerable.

I think this system has the ability to be broadly useful, especially for non-experts. However it isn't perfect. Firstly, while it technically applies to all light sources (displays included), it is most relevant to lighting such as bulbs and lamps. There are likely screen-specific flicker effects that haven't been described yet. Also, it mainly predicts the visibility of flicker artifacts, which are visual disturbances, not health effects. I think flicker artifacts and visual disturbances may be correlated, but there is not a one-to-on relationship.

Thanks to u/Rx7Jordan for making me aware of this standard.

I've been looking for a decent phone that I can replace my current iPhone 16 with, since I can only tolerate it for a few minutes a day. I've been looking at a lot of OLED test reports, and I think I've noticed a problem with many of them: the measured flicker is falsely low, since the photodiode is measuring multiple OLED rows at once. In my opinion this results in a loss of information about what the screen is really doing.

In some extreme cases, I've seen devices which actually have 100% modulation depth be measured at ~5% modulation depth. All the OLEDs I've measured with this method (using my meter or the Opple) actually show 100% modulation depth at all brightness settings. I'm not confident this is true for EVERY device, but I think there are a lot of measurements online that underestimate the OLED flicker.

I showed this in the video, but to avoid this error you simply have to reduce the number of OLED scanning rows that the flicker meter detector is exposed to. Ideally, we'd only measure one row since this contains all the relevant information. In practice multiple rows are needed to get enough light onto the detector.

For me, it might be time to just buy an e-ink phone.

I created a visualization of how many OLEDs actually flicker and use PWM: https://www.sundiallabs.tech/pages/oled-flicker

I made this because I was inspired by a post by u/NoFlickerPhone, who made a great PWM simulation webpage. The goal of my page is to explain how and why OLEDs flicker, and also describe how to properly measure OLED flicker. I've been doing lots of flicker measurements on OLEDs lately, and it can be confusing to get right. I've also seen lots of PWM test results on OLEDs that were not done completely correctly and end up underestimating the flicker depth. Incorrect results are especially common to see at high / moderate brightness.

The first visualization shows how the dimming works on mobile OLEDs, specifically modeled after the iPhone 17 Super Retina XDR OLED. It appears to use DC-dimming for some of the brightness range, then switch to PWM. This is done because most OLEDs can only be DC-dimmed to a certain point.

The second visualization explains why OLEDs need to be measured carefully. The basic idea is that if your measurement device is detecting light from multiple rows, the waveform will be "smeared" or averaged and the flicker will look less bad than it actually is. This averaging isn't what our eyes do (they form an image of the screen which preserves the flicker pattern). So ideally, we need to be measuring the flicker from a single row (or only a few adjacent rows).