Apple miniLED Products (2021)
Seagull I know you're a fan of the LCD inversion theory as the root of many issues - would a mesh of LED backlights have any impact on this or is it purely the LCD that causes the inversion flicker?
While I've got you, I also wanted to ask if you believe that the same panel could have different inversion characteristics depending on the GPU / GPU driver being used? As I am now able to successfully make 2 machines I own 'good' or 'bad' almost instantly. Thanks!
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A mesh of LED lights won’t affect inversion, that’s solely within the lcd panel.
Onto your second question
[LCD Inversion]
First let’s re-examine what LCD inversion is. Liquid crystals will degrade if you apply a constant current to then. So to prevent this degradation every frame the voltage is switching from + to – or – to +. If this switching was perfect we wouldn’t see anything changes, but in practise these voltages aren’t perfectly aligned so the crystals shift every frame.
So every frame some pixels get brighter, some get dimmer. The next frame, they swap so the dim ones become bright, the bright ones go dim. It creates a kind of flickering effect at half the frame rate of the panel. Its half because it takes 2 frames to complete the cycle bright->dim.
All LCDs will do this, though it will be weaker or stronger depending on the inversion implementation. I personally think that panels with higher pixel density will be worse, as smaller pixels mean smaller electronics and more variation and slacker production tolerance. So I expect laptops to be worse than full size monitors.
[LCD Inversion + Superposition of Dithering]
So getting back to your original question, how can you make a good setup bad? Well let’s compare inversion with temporal dithering. In temporal dithering pixels are going from bright->dim etc just like inversion. But they aren’t necessarily doing it at half the panel frequency. I found in my testing that whilst some pixels may be dithered every other frame, others might only change every 60 frames, or longer. So temporal dithering is displayed at simultaneous frequencies between 0hz and half the frame rate of the monitor. A kind of broadband flicker.
I think that the broadband flicker of temporal dithering might be an effective way of breaking up the half frame rate flicker caused by LCD inversion.
So back to changing setups. If you change the colour profile, you will be changing how temporal dithering occurs. Basic white (0,0,0) could now be offwhite (0,0,1) which was previously dithered at x hz might now be dithered at y hz and that could feel better or worse. Changing a GPU will give an entirely new temporal dithering algorithm. Changing from digital to analogue display outputs will have an effect as interference will make VGA fuzzier (more broadband flicker). Perhaps a windows update changes how alpha channel is processed and that has a knock on effect on dithering and colours.
The next question then, is why would a broadband flicker be better than a fixed frequency flicker? Or even, why would one fixed frequency of flicker feel different to another?
[Migraine Theory]
To examine this I will touch upon the field of migraine theory, which is undergoing something of a renaissance at the moment. The first important concept: migraine has recently been characterised as a protective measure for the brain, a kind of emergency shutdown to protect the brain from over exerting itself and causing damage. Following the shutdown changes in brain chemistry consistent with increased repair and growth are seen https://neurosciencenews.com/migraine-oxidative-stress-7761/.
The next important concept. Migraines are now thought be triggered in response to brainwave synchronisation. To understand this, you need to know that the brain operates with repeating pulses of electrical activity – kind of like how a CPU operates in clock cycles. And that the faster you think, the faster the frequency of these pulses. Also be aware the brain is not like one big CPU, different parts of the brain perform different functions (vision, movement, hearing etc) at different speeds. So your brain is more like a hundred different CPUs operating independently. Problem is, if one ‘CPU/bit of your brain’ is running particularly fast, that speed can spread to other parts of your brain – even though the parts of your brain its spread to have no processing to do. A migraine can be triggered as an emergency shut down to stop your brain wearing itself out when this occurs https://www.aps.org/publications/apsnews/200405/migraines.cfm.
So you are staring at a 60hz LCD screen. Its flickering at 30hz due to inversion. The visual processing part of your brain has now matched this frequency and it too is operating at 30hz https://www.jneurosci.org/content/39/16/3119. This could spread to other parts of your brain, triggering a migraine as an emergency shutdown measure to prevent damage from overstimulation.
What if you don’t get a migraine? There is a genetic component to migraines, so some people just don’t get them. Well, 30hz brainwave corresponds to normal but intense brain activity https://www.scientificamerican.com/article/what-is-the-function-of-t-1997-12-22/.
So perhaps rather than a migraine, these people get normal headaches due to their brain over exerting itself. Perhaps they get facial twitching because the part of their brain that controls those muscles is now operating at 30hz when it should be idle. The symptoms of your brain overworking itself could be anything really.
[Experiences]
This brings me onto something I think about a lot. Why do people hate intel graphics so much? I think it’s not because intel graphics dither (they don’t, I’ve tested lots of them). I think people get pain from intel graphics because they are not temporally dithering! So they are seeing a strong half framerate flicker, undiluted by temporal dithering. Something I think will be worse on laptops where their high DPI screens will have more voltage irregularities creating a stronger LCD inversion flicker.
Personally, I have a monitor that I can only use with GPUs which dither. If I hook up my non dithering intel GPU I get pain. The above is the best explanation I have for that.
Seagull Amazing post Seagull!
Do you think you are sensitive to pixel inversion? Did you try to connect a bad device to an OLED panel? because in this case the pixel inversion should be fixed and also your problem.
For some reason i've never felt really sick with OLED devices, maybe it's just luck or maybe not?! OLED panels emit less blue light than LED panels, no LCD inversion and 0,1 ms G2G. Could the faster pixel response time help with dithering?
Thanks, I've been planning on posting something like that for a while.
I think I am quite sensitive to pixel inversion in IPS LCDs, but less so with TN. I always get a migraine with an IPS display, unless it’s a high DPI display and I am sitting far away from it. I don’t yet have any evidence for why though. I was thinking of building a high speed camera so I could see inversion and how it differs across different panels but I probably won’t on account of the amount of time it’ll take. I might buy a high refresh rate IPS monitor and try that out. I could set the framerate to 240hz, 120, 60 etc thus changing the inversion rate, and seeing what the effects are.
OLEDs are quite different to LCDs as you point out. One important feature is that they flicker at their refresh rate. A 60hz OLED flickers at 60hz because each pixel goes dark every frame as it updates to the new frame. I’ve never gotten a migraine from an OLED, but I do get headaches. I wonder if that’s because of the higher frequency flickering. Maybe if I get a 30hz OLED it’ll give me a migraine. Or maybe if I get a 120hz IPS LCD (therefore with 60hz inversion flicker) it’ll feel like a 60hz OLED and I'll get a headache instead of a migraine.
I also think the faster response time could be important with OLEDs. An IPS LCD response time is more like 20ms, and due to irregularities across each pixel it’ll be different for each one giving a fuzzy effect as one pixel responds faster than another and so on. Because of inversion having every frame regardless of whether anything changes on screen, that fuzziness will always be present.
bkdo if there's any potential for long-term or permanent damage
I really don't know. The brain is just such a pandoras box of weird stuff. Take a look at this for example.
https://www.sciencedaily.com/releases/2020/02/200203141446.htm
Flickering light prevents Alzheimer's disease in mice, and different flickering frequencies had different effects. As much as it hurts, looking at flickering displays could even be good for our brains long term.
iPhone 13 is rumored to have LTPO display, similar to the apple watch.
I don't have any issues with the apple watch with LTPO.
https://www.macrumors.com/2021/04/20/new-ipad-pro-with-m1-chip/
"As was widely rumored, the display uses mini-LED backlighting with over 10,000 LEDs to deliver true-to-life HDR content."
It may be a long shot, but I'm interested in seeing if the mini-LED screen is any better in terms of flickering. I'm going to order one and test it during the return period, will definitely post my impressions when it's out.
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Seagull It’s a very well-thought post of yours. However I'm not really sure about the last part of Intel HD not dithering. In my case which is an HP laptop, anytime I go back to the Intel HD driver (from the basic display driver) the colors just totally change, especially white color. Like it is not a solid, static white but becomes a mess of hue, rainbow like colors mixed up to reproduce white, that can not be fixed with any setting. If you tested and saw that Intel HD does not do dithering then it is really strange; is there anything else that it can do differently to the display?
FNP7 Someone did end up getting the iPad Pro early, I asked if he would do the standard slo-mo video test and here was his response:
"I could not get my phone to record a long enough video in slow-motion in order to go through all of the brightness levels. I am one of the few that are sensitive to screen flickering and I haven't noticed anything at any brightness level. The only thing my phone picked up was when I was within the 10 to 15 percent brightness range and lower, horizontal lines appeared, but no flickering. "
Also, I'm grabbing one on Friday. I'll definitely update with my experience.
https://youtu.be/0SwTkETENLI?t=369
slow-motion video
daniel5489
Thanks for sharing the vid, glad someone is talking about the flicker.
He said:
"When it comes to flickering, the mini-LED screen is not as flicker-free as the regular LED screen, but compared to OLED, it is much better. And so far, it hasn't triggered my ocular migraine, and I also don't think it will."
That's not super encouraging, considering that a lot of people get symptoms from other Apple devices with regular LED screens. Glad it works for him though, seems like it's a step forward from OLED at the least.
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TLDR: The miniLED screen is better than OLED on my eyes, but still causes eye strain. I suggest trying it yourself, it's definitely a step forward IMO.
So I've been using the new iPad since Friday, here are my impressions eye strain wise:
-Slow motion video of the screen shows very little (If any) flicker, nothing like OLED flicker.
-It doesn't seem to have that "shimmer" effect that I usually get from Macs.
-The eye strain from this iPad is much less harmful than Macs/OLED iPhones, it feels like a slight prickling above my eyes after some use, but no migraines (yet)
-I don't really notice any huge flicker difference between brightness levels.
I'm very sensitive to flicker, so just because the miniLED screen bothers my eyes doesn't mean you guys shouldn't try it. It's definitely a step up from OLED and the Macs IMO, I think it's worth a shot to try.
I'm going to try messing around with brightness/white point/night shift/true tone a bit more to see if anything helps, I'll post my results in a few days.
Seagull
This is also my belief. I posted about my Philips monitor, that monitor was flickering like crazy in the lagom inversion pattern test. It caused me such a strong eyestrain that i saw real life zig-zag noise pattern at like 30 HZ after using that monitor... It was 100% that monitor causing it(never seen anything like that since im using different monitor, its crazy that they sell garbage like that, it should be illegal to sell products like that monitor), and its either came from inversion or it come from color dithering.
I had a TN LG monitor, that had very crazy inversion too, i could see the pink/green discoloration thanks to the inversion, it was very strong effect, but that monitor was still easier on my eyes than the ips Philips. I could tell that the image was not stable, but it didnt cause such a hard eyestrain for some reason. Maybe if was obvious for my brain(green and pink pixels flickering), that it didnt try to fight it, unlike with the Philips product where my brain tried to compensate/fight the constant flicker...
Currently im using a Dell monitor which is ok most of the time, its not flickering in the inversion pattern test. But on dark/gray colors, its instantly triggers some kind of anxiety attack. I think this is maybe because the 6 bit FRC flicker + the very low contrast of the IPS panel that causing it.
I wrote about my Mac M1 experience in detail here. Today I went to a local Apple store to test new mini-led iPad M1.
At first I looked at a couple iPads that turned out to be old models. They felt OK to the eyes. Then, the staff showed me to the iPad M1. This works like magic, guys... A MERE GLANCE at this screen triggered my strain. I tried to have a better look at its interface but couldn't last for more than 3-4 minutes. Now, another interesting thing. There was another mini-led iPad with smaller screen. The note said it used A14 chip if I'm not mistaken. And, surprisingly, it felt much better. I still experienced some after-effects after M1 iPad at this moment, though. Should give it another isolated try.