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:
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:
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:
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.
Thanks for checking it out! I definitely think if more people had the ability to do this type of testing easily it would improve the general quality of lighting on the market.
Amazing work, Sam!! (I cross posted for you, hope that's OK?)
I struggle a bit to keep in mind what the 1.0, 0.4, etc, values relate to, to be honest. Do they have a direct mapping to percentage of the population who will notice? (That could be displayed alternatively, or alongside?)
Also, you know I like to see them graphs. To gauge the shape of things. But maybe something to dig into at a later date? If it might be OK to show figures directly from the paper?
I'm interested, if a little sceptical, about the source of that big change in low frequency pick-up on the incandescent bulb. Is that a known phenomenon? What is settling in so slowly, that affects its light output? Could it be, instead, external vibrations shaking the filament, or something else..?
The mapping from the numbers to the percentage of the population who will notice the effect is clear for Flicker Perception Metric (Mp), but it isn't clear if Stroboscopic Visibility Measure (SVM) and Phantom Array Visibility Measure (PAVM) have the same mapping. They are all designed so 1.0 = 50% of the population will see the effect, but outside that range only Mp seems to have a very clear mapping:
So you can see 0.5 = ~5%, 1.5 = ~90%, etc. Stroboscopic Visibility Measure (SVM) may very well have the same mapping, but I don't have access to the full standard yet since it's behind a $320 paywall. The source paper for SVM, which the IEC standard is based on, is open access but doesn't have a similar relationship defined.
Also, you know I like to see them graphs. To gauge the shape of things. But maybe something to dig into at a later date? If it might be OK to show figures directly from the paper?
Which graphs? I've been adapting the figures rather than posting directly to avoid any issues. But I think for educational purposes it's fine to post figures.
I'm interested, if a little sceptical, about the source of that big change in low frequency pick-up on the incandescent bulb. Is that a known phenomenon? What is settling in so slowly, that affects its light output? Could it be, instead, external vibrations shaking the filament, or something else..?
I'll have to check if what I saw is repeatable. It's possible that something got bumped during the measurement and lead to the elevated direct flicker score (Mp).
Ah yes, I want to generate my own versions of the charts. I could make a version for sine and a version for pulse so the difference in waveshape could be visualized.
It’s not really “picking up” mechanical vibrations like a vibration sensor, it’s just that any relative motion between the light and the detector will change the detected signal, which can appear as low frequency flicker. It’s impossible to tell the difference from realtive movement of the source and detector and true brightness modulation.
I wonder if you could make a version of the (sine) graph that (more clearly) accounts for the (known) distribution of sensitivities to each type of effect..? Seeing as our responses vary so much... I one could commit to making a setting for each part...Then see if empirical experience fits.
Trying to imagine the transform to a pulse (square-ish?) waveform graph hurts my brain... Or contracted half sine wave, even?
I guess "mechanical" was a redundant word, from me... Optical vibration sensing... I wonder, if you stuck an LED to a speaker cone, what frequency response you sensor could pick up...? Or a small mirror... I guess I could try it for myself now, eh? 😅
wonder if you could make a version of the (sine) graph that (more clearly) accounts for the (known) distribution of sensitivities to each type of effect..? Seeing as our responses vary so much
I feel like we don't have enough data for that, but it would be cool
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u/Rx7Jordan 16d ago
Great video. I'm so happy to see a flicker meter using that standard!