martin Yesterday I screw up with AMD driver modification (every time I set CFG_NO_DITH - I can't restart machine anymore, stuck on logo, about 70%)
The way to fix is to load in recovery mode (holding command+R) and copy unmodified kexts from recovery partiyion to your /System/Library/Extensions/
Here I did screenshot of commands I use for restoring original kext:
https://ibb.co/Gt0X1YH
Gleb I cant even get the first command in terminal running - kextstat | grep Intel
Martin-MacBook-Pro:~ martinjanas$ kexstat | grep Intel
-bash: kexstat: command not found
You are probably very experienced and so certain things seem as given, is there more dumbed down version of how to do this?
Also how about installing windows 10 via bootcamp and trying to disable all of it there to see if it indeed helps your eyes? Could you do that and share the process? Its good testing ground as its easy to wipe it if it goes wrong and still keep macos intact. If it works there, then its good motivation to figure it out for macos.
kextstat | grep Intel
That was a typo somewhere
Windows
I do not have much free space currently for it. But even in MacOS flipping integrated\discrete card switch makes a HUGE difference in how fonts and colors looks. Also now it is relaxing on eyes (my gf also see a difference with and without dithering)
Gleb Okay so I've got the Mac powered on - disabled csrutil first then restarted.
My drivers loaded look quite different - https://imgur.com/uKdcGfz
diop Unfortunately I do not see this hidden parameter for FramebufferCapri:
You may try to set Dither instead of mine DitherDisable
number = 0 to disable it, if I understood Framebuffer code correctly
But I can't promise results. Still worth trying.
In the meantime, I wonder if you install SwitchResX https://www.madrau.com/srx_download/download.html
And reduce colors to Millions of color, instead of billions https://ibb.co/44P4CDQ
AND, more important, in System Preferences -> Display -> Color, select Generic RGB Profile instead of Color LCD https://ibb.co/hXz3JmG
Then it seems to disable (or at least reduce) dithering effects.
You can verify it on gradient image http://www.lagom.nl/lcd-test/gradient.php
It should look banded, not linear gradient as here: https://ibb.co/PY4PZ71
Can you try it and share the experience?
Gleb So initially after trying to follow the instructions I realised I didn't have Xcode installed. I tried to download from the App Store but it required that I upgraded AppleOS. So I've upgraded the system to latest Catalina.
The Grep | Intel list looks the same > https://imgur.com/jjJorY8
However when trying to allow permissions to the Directory/plist file it said something to the effect of 'read only directory'. I ran csr disable in recovery after the Catalina upgrade, so maybe there's another security feature that needs to be disabled first?
I opened the plist file direct in Xcode here > https://imgur.com/HwYyZkD - but I couldn't find any FeatureControl option.
I did change the colour profile to Standard RGB, but didn't install SwitchResX.
Here is a pic of the test page > https://imgur.com/JLWqC1B - I can see a gradient which is strange.
If there's anything you can suggest I will give it a shot - thanks for your help so far. (Glad to know it's working for you at least).
diop
You need to navigate deep in that plist file: IOKitPersonalities->AppleIntelFramebufferController->FeatureControl
FeatureControl is a sub-section 3 layer depth from the root. See my picture again: https://ibb.co/dgqK0MS
For the file permissions, you may try right-clicking on plist in finder->get info 
And add your account to this list
fyi.. with AMD+Displayport you can turn off dithering in the control panel (select 6 bit color)
Gleb After a bit of searching online it appears that from Catalina onwards kexts have to be signed by Apple in order to work, also I think the file system changes mean system files are permanently read-only regardless of SIP being switched off.
I downgraded to Mojave and installed Xcode - I made a slight mistake editing the plist and couldn't see a way to undo changes (doh) so will start over tomorrow and try again. Presumably I right-click FeatureControl and 'Add Row'? Then enter the details like you mentioned 'Dither' value '0'.
Do the changes happen immediately after adding the line or does the system need to be restarted first?
I updated to Catalina (10.15).
I checked decompiled code for AppleIntelCFLGraphicsFramebuffer, and they still have DitherDisable hidden option
For Catalina there is additional step needed before they allow editing Plist inside kext:
sudo mount -uw /
I checked logs with command
log show --predicate 'processID == 0' --last 1h | grep Intel
https://ibb.co/TmCqKRb
and
log show --predicate 'processID == 0' --last 20h | grep Dither
https://ibb.co/WzjyHGH
BUT
I think things are looking a bit different.
Previously (on 10.14) when I was switching to High-Performance, I was noticing immediate changes in font rendering and color balance (they looked very strange on AMD).
Now there is no visual difference between Intel and Amd graphics. There are 3 possible reasons:
DitherDisable option is no longer working in my FramebufferI will need to look at my screen for a day to see how it works.
ever visited a good optometrist?
In the end, martin may be right about this, and I just have aging symptoms (I'm 28 now, work on computers since 6). The reason why I think this might be an issue: I booted Windows PC (with AMD 280x card), disabled\enabled Dithering in registry, and didn't notice any effect. Only thing I see is kind of visual snow (and that is the first symptom for CVS).
Also I wonder if @JTL is able to connect the capture card to one of DP output? And record video of signal from mac.
Also, if anyone here does have android eink reader, https://youtu.be/lWAsfZTUrJs?t=560 it might be possible to test screens for dithering using VNC (in theory, without buying expensive dasung). I will try to do such tests, but currently, I do not have eink on android.
Gleb Its not related to aging as much. Id still like tech solution but the vision therapy helped a lot too.
In switchresx, it seems millions of colors is actually a basic macos setting, and billions is something thats extra in that program. So switching to millions doesnt do anything different from the base macos setup - https://discussions.apple.com/thread/3614614
therefore wouldnt probably do anything with the dithering.
I tried to recap what changed in past year, and at some point (6-8 month ago) I changed display brigthness contrast to
Brightness = 100
Contrast = 30
That was because I was doing some web-design and couldn't distinguish between shades of gray. So I worked with MAX brightness for more than half of the year.
Reading about CVS (Computer vision syndrome) I realized that 100% brightness is too much - eyes are exposed to w-led which causes eye strain (?). Maybe it is the same as looking at the sun or a bright lamp
So I dropped my Brightness to 20, and raised contrast to 70:
Now, letter edges are sharper, and the overall perception of the screen is more relaxed. Also, I no longer notice visual snow.
Hope this advise will help.
Gleb I did a fresh Mojave install / installed Xcode and then performed the steps as above. Added a row with Dither > 0 and restarted. I don't think it has made any difference to be honest.
Are there any other kexts that need changing or any other way you know of that OS X enables dithering?
Also AFAIK the Intel linux driver is open-source. I'm sure others here would also be interested to know if a Linux dither-disable is something that could be implemented.
Basically our aim (or certainly mine) is to 100% disable dithering (be it Windows/Linux/or Mac) to rule out the negative effects that may be caused by it. We can't rule it out as the root cause of our problems as we can't knowingly disable it or know if/how it is currently in use.