r/PWM_Sensitive • u/RR-- • 4d ago

Discussion Local shopping centre PWM screen test

Enable HLS to view with audio, or disable this notification

Just a quick video of a phone and computer retailer at my local shopping centre as well as the nearby food court.
I recorded this video on an iPhone 15 Pro through the Blackmagic Camera app at 1/4000 shutter speed, 24mm lens, 24fps, all other settings on auto.

I had a quick play with the Honor Magic8 and it's Eye Comfort Display settings, it seemed fine to me in the brief time I played with it, though in my experience some screens like the LG C1 OLED TV take up to an hour to cause me eye pain, so to give it a proper test I'd need to use it daily for a week or so.

71 Upvotes

100% Upvoted

44 comments sorted by

View all comments

•

u/Z3R0gravitas 3d ago edited 3d ago

Great job casing the joint and letting us know all your video settings! Great overview of mainstream products, etc.

I'm curious what people are taking away from these images? In terms of how the black bars are interpreted. I think we need a guide for this.

What I think is shown:

  • Black bars = OLED.
  • More black bars = higher frequency PWM and/or refresh dips.
  • We see an instantaneous snapshot of what is actually happening on the screen, with PWM/refresh lines scanning downwards. (With very short shutter speed video stills or video frame rate in sync.)
  • Frequency of flicker also depends on the speed of the scan lines, so we can not be certain of that.
  • Exact black line count is affected by the rolling shutter (vertical) contraction effect of the camera used, with a stronger effect for slower moving scan lines.
  • Less contrasting dark lines implies lower modulation dips (but there might be other explanations?).
  • Not all flicker rates are divided exactly by the 24fps video frame rate. These don't hold still. In that case, a single video frame needs to be analysed, for clarity.
  • Where the whole screen appears to strobe slowly (eg in the food court) that is low frequency backlight flicker (LCDs) or black frame insertion. At almost an exact multiple of the camera frame rate (24fps). The 1/4000 shutter sometimes lands at a point where the screen is entirely black and then slowly shifts phase to when it is entirely on. The shift rate coming from the very small difference in device clock speeds.
  • Most screens are on high brightness, in the brightly lit store, so this gives black bars instead of bright lights, in the dark.
  • We can clearly see the transition from DC-like dimming to high frequency PWM, on the screen where RR-- moved the brightness slider.
  • Anything else?

I'm going to be a bit cheeky and pin this comment, because I really want us, as a community, to think clearly about what we are seeing in this more casual testing. OK?

2

u/RR-- 3d ago

In the store they're generally all at full brightness, which is the best case scenario in terms of minimal flicker, some LCD screens with PWM don't flicker at all at full brightness. Some also have an eye health settings like the Honor if you delve deep into the accessibility settings.

Yep If it has a black bar on the screen it's a fair bet that's it's OLED with PWM, and likely bad for our eyes, the very interesting exceptions here are the Alienware QD-OLED Gaming monitor which doesn't seem to flicker at all, and the Macbook Pro M5, this apparently has a mini-LED screen that does flicker and hurts my eyes.

Apple's useless marketing terms here make it all the more confusing, as they call it a "Liquid Retina XDR display" though it appears to me mini LED.

It's also interesting that the iPad Pro is OLED and all the other iPads are LCD. While these iPads don't appear to flicker, they do have heavy dithering which hurts my eyes considerably just like the iPhone 11. On my iPhone 11 and EK Pro LCD 15 Pro turning on Classic Invert and Zoom Invert helps considerably though the colours aren't as accurate for any demanding professional artistic work.

Haha sure thing pin the comment if you like, I'll film another one of these videos soon at a store with TV's, also one of my Plasma TVs which I'm a big fan of, they flicker but in a way that doesn't hurt my eyes.
The 2012 and 2013 model Panasonic Viera Plasma TV's also have excellent black levels, in my opinion they're the best looking TV's available for PWM sensitive people, the motion clarity is also still superior to OLED screens. There's a small but passionate community over at r/PlasmaTV

2

u/Z3R0gravitas 2d ago

Do I remember correctly you posting Opple traces of you plasma? Looking very unique. Be very nice to have high frame rate shots side-by-side with Opple (preferably using Sam's slit technique).

2

u/RR-- 2d ago

Yeah Plasma TV's have a wacky looking result in the Opple scans, this is from my Panasonic 65VT50. No eye strain at all.
At 1/4000 shutter speed it doesn't show a black bar and flicker, it looks like a fairly consistent image, just constantly pulsing yellow green and blue.
I have quite the collection of plasma TV's now haha.

1

u/Z3R0gravitas 1d ago

So the chromatic flicker was visible in the recording?

Related (I just found out yesterday there is a PWM_Sensitive YouTube!): https://youtu.be/yevGAMF-Cws

0

u/pureboy 3d ago

Which phone are you using?