It is an over-simplification, but it might help to consider that a 30ms response time would equate to about 33frames per second (or Hz). If that monitor has a nominal refresh rate of 60fps (or Hz), then it may not respond fast enough to show any dithering.
Its kind of similar to the argument where ccfl pwm is more tolerable than led pwm because the rate of change of colour is slower and not instant.
Seagull I was thinking more about this and looked up the specs on my current "bad" panel in a Thinkpad..its an LG LP140WF3SPD1 and PWM free, and has a 25ms response time according to panelook.com but this laptop is still straining. I have put all sorts of panels in it from TN to IPS and everywhere from 5ms or so to 28-30ms with no success. So that feels like it can't be related to response time. Although as you know there are so many other factors who knows what combo is the trigger.
Seagull It is an over-simplification, but it might help to consider that a 30ms response time would equate to about 33frames per second (or Hz). If that monitor has a nominal refresh rate of 60fps (or Hz), then it may not respond fast enough to show any dithering.
It resembles the article I have linked in one of the other threads: https://www.lifewire.com/lcd-displays-and-bit-color-depth-833083 - they claim there's a clear relation between bit depth and response time of screens. Anyway it's hard for me to believe that every panel with over 8ms response time is 8 bit since almost no notebook panel is faster than this as I browse Notebookcheck reviews.
andc Anyway it's hard for me to believe that every panel with over 8ms response time is 8 bit since almost no notebook panel is faster than this as I browse Notebookcheck reviews.
I have spent a lot of time looking at panel specs on panelook.com and nearly all laptop panels I have seen are not true 8 bit panels but rather listed as 6+2 meaning 6 bits plus using dithering to get 2 more bits for a total of 8. For example here is the HD panel in a 2018 X1 Carbon http://www.panelook.com/B140HAN03.1_AUO_14.0_LCM_parameter_32138.html It just says "6+FRC" but many say explicitly "6+2 FRC"
Even the fancy HDR panel on the X1 Carbon 6th gen seems to not really be 12 bit HDR as it is advertised but rather 8+4. IF dithering is an issue then this is super relevant because most laptops are only 6 bit natively but being told to show 8-bits. But since laptop panels are "dumb" and require the gpu to tell them to dither I hope that means we can somehow force the output to the native color depth so the dithering doesn't happen.
But as usual it's confusing because IF dithering was the root cause it would seem logical to think an older 262k 6bit TN panel would be strain free and in my experience it is not...but to be fair I was unable to find one without PWM to avoid that variable. I don't know if that means those panels are still capable of dithering above 6 bits or if something else is going on.
Wow, I didn't know that this site contains such details. That's great that we can see what the actual bit depth of panel is if we know the model - thanks a lot.
Regarding PWM - I tend to believe every panel nowadays uses some kind of flickering - either as a whole and/or on individual (sub)pixels level. Actually I find panels using PWM better at first - the picture seems to be more stable, there's less snow, of course at the highest brightness setting. The ones that are supposed to be PWM-free (at least my phone doesn't see the lines) start causing issues within a matter of seconds / minutes. So I think they may employ some micro-PWM-like mechanism that doesn't look like on/off on oscilloscope tests, but the whole screen works all the time, especially when brightness gets reduced - something which I observed under microscope on lower brightness levels.
andc Unfortunately that site doesnt list PWM use as its info comes from manufacturers and they don't want to share that with anyone it seems. "Flickering" is a broad term and PWM backlight flickering is entirely different than dithering/FRC, but who knows if the results with regard to strain is the same or not. My personal experience has been that PWM is irrelevant since using known PWM free panels causes the same amount of strain as ones with visible PWM. It surely can't be GOOD for us but I've never seen someone solve their strain by simply removing PWM.
Sure, but at least low PWM can be easily tested with phone, and there are many reviews by Notebookcheck that cover various panels, so mixing results we can find panels that are 8-bit without FRC and PWM-free. That doesn't guarantee anything, but at least that's less enemies to defeat.
andc For me at least it doesn't matter if they are PWM free and 8-bit. I have seen such panels at shops and they still strained me. The Dell XPS 15 is an example. That's what makes the dithering thing confusing because if that IS a major factor then why would it be happening on a true 8-bit panel? Does that mean dithering isn't a cause of strain? Does that mean it's trying to dither even higher to 10-bit etc?
hpst
As usual, we can only guess, and try to find a needle in a haystack. I've been also thinking about refresh rates, frequencies, etc. For example I have some ear issues where particular frequencies tend to cause me physical pain (probably due to many years with headphones, etc.). There seems to be a relation between eye strain, sinus / jaw issues in some cases, both of them have also effect on ears. The pressure I can feel from staring at some laptops resembles sinus pain. So maybe our eyes are sensitive to specific frequencies, the same as ears, and these frequencies might have changed in recent years - due to dithering, new technology, more powerful gear, etc. Since we have different sight we may be sensitive to different frequencies - that would explain why someone can't use PWM screen with low refresh rate, while it doesn't bother other people. Just a thought, one of options.
JTL We are on the same page I think...I may have just expressed it wrongly. The laptop panel doesn't have built in dithering instructions or blue light/contrast/brightness whatever etc like a desktop monitor can so I called that a "dumb panel". As I understand it the panel's pixels have to "dither" to get the "super awesome vibrant" colors and thats what I meant by saying the gpu is making the panel dither. I understood the gpu is making it happen.
JTL Nearly every BIOS screen I have seen is on 100% brightness with no ability to reduce it so I can't stand looking at them just due to that...it's blindingly bright and hurts on anything but a super old dim CCFL. A 2014 Thinkpad I got for testing did surprisingly allow brightness controls to work in the BIOS but an update ruined that.
What does that mean? Why in the world would a text only, pre OS utility be dithered? Does that mean its just hardwired into the gpu and whenever a computer is on its dithering regardless of what is displayed? I had some hope it was dithering because instructions in the OS/drivers were telling it to which would mean it might be possible to turn off. If its in firmware before the OS and drivers even get loaded how could we even affect it?
deepflame Teradici (a company that makes display over Ethernet extenders that use image compression which dithering interferes with) claims that the 10-bit color option on certain AMD graphics cards can disable dithering. So that's another datapoint.
This could be huge as an easy DIY test to see if dithering is or isn't an obvious problem. Do you have any more info on what gpus? There isn't any detail. I see there are linux instructions there which was a nice surprise as I thought "yeah it probably only works on Windows". If this would work on AMD Ryzen/Vega laptops etc it would be an easy test as there are a couple at Best Buy I could try in store if this Catalyst Center thing is normally installed...but they have locked down internet so no installing new stuff there.
Do you know if you can enable 10-bit monitor support, thus turning dithering off, on a Linux system with an AMD GPU/APU somehow? I could also live boot linux in a shop and try that as well. Worst case I would buy an AMD laptop and just return it if it didn't work...but I guess I need to know what GPUs/APUs this works for first. Does Nvidia have a similar process since there are a lot more Nvidia models out there to test?
