Yesterday I applied nvram boot-args="dither=0 enableDither=0" from terminal utility in recovery mode and there are some interesting artifacts noticeable now.
When watching videos on YouTube, or when viewing images in general, there is a slightly smoothened experience. This is very similar to a very light noise reduction applied. Everything feels like wax coated or extra smooth. But the difference is subtle, only noticeable if we pay attention to it.
The text and other non-media content looks basically the same. The busyness of white background may or may not have improved but is very difficult to discern. It is only subtly noticeable in media content at this point.
I checked the pixel shimmering at 240fps again and it is there, nothing has changed. But there is indeed something different after I made that nvram setting change, that's for sure.
There is no color banding before or after the change, on both UP2720Q and the built-in screen. Everything was driven by the discrete AMD card all the time though.
This led me to different conclusions and also questions some of the concepts being discussed in this forum in general.
The main conclusion is, using a microscope and high-speed recording may not be the right way to detect dithering in LCD-based displays after all. LCD has to switch polarization every other frame so that will overshadow any additional pixel switching introduced by the dithering. We won't be able to visually distinguish these two switching patterns.
Another assumption is, if a panel says it is 8+2FRC, that is supposed to be the panel spec, meaning the panel circuitry is supposed to take care of the 2FRC part and whoever is sending data to the panel, it appears like a 10-bit supported panel it is sending data to. I didn't see any 8-bit banding on the built-in screen after I applied the nvram settings. So I suspect the panel still received 10-bit data and did all the FRC internal to it, using its own circuitry.
So that raises the big question of whether dithering was indeed disabled. I don't think dithering was disabled. No Mac laptop screen panel is natively 10-bit capable. And I don't see any 8-bit banding whatsoever. I checked a lot of different media like images and video, no banding. So that means dithering is still indeed happening.
But I did see some new artifacts after the nvram setting change, mainly the effect of de-noising, although a bit subtle. So this is where things get really intriguing. We know dithering is also used in audio, not just video. Dithering in audio is the mixing of noise to avoid quantization errors and making low bit rate audio free of audibly detectable artifacts. Now if we translate this to video, we know image compression like JPEG worked by using quantization and taking advantage of the way human visual system works. So this is my theory: there has to be a hidden way of doing something similar to adding noise to audio, to make the quantization artifacts in the video or JPEG compressed images less noticeable to the human eye.
So there has to be some totally other objective here behind adding dithering in the source via a graphics card. I guess we are mostly stuck on the idea of color depth management when we hear about dithering. What I see is, this could be simply achieved by the panel circuitry itself, while the graphics card is doing much more than that, working hard to apply different methods of reducing perceivable quantization. Also this can be a big deal for companies like Apple, making sure their laptops are not displaying wax-coated content as opposed to clear and crisp content from others.
Now what is it really playing out when it comes to health? I don't have many ideas, but I have some theories though. If the basic method here is to add random noise to make the quantization errors less perceivable from compression, then we humans are presented with a lot of junk visual data than there is in the original source. And here is the important aspect of the theory: we may be presented with a lot more junk than our brains need to process. This could be a bit overwhelming for some.