I disabled dithering on Apple silicon + Introducing Stillcolor macOS M1/M2/M3

Donux It is modulation depth, so 15006 times per second the brightness drops 79% when looking at a pure blue background. The question is why that doesn't happen with red. If this was simply the backlight flicker (not PWM) then at least for me it makes no sense that it doesn't affect red.

Could it be that KSF phosphor that is slower to respond causes this?

https://pcmonitors.info/articles/the-evolution-of-led-backlights/

Just thinking as I type here, and I'm probably butchering the explanation and understanding of the visual system. A lot of how the visual system works it is built around opponency of the following types.

• High / low luminance (black / white)
• Red / green
• Yellow / blue

Basically our vision detects a shitton of edges and gratengs thru these combos.

What actually happens if red doesn't flicker (due to KSF phosphor) while green that hit the M and L cones does?**

We have some rods that mainly respond to brightness (black and white), and we have 3 types of cones that maps to different colors. The type of color and input can make us use certain visual pathways more or less. So looking at large slowly moving black and white blobs will take a different path than looking at colored details.

Some quick info on the 3 pathways:

Magnocellular (M) pathway:

• Processes motion, depth, and coarse visual details

• More sensitive to low spatial frequencies and high temporal frequencies

• Plays a role in detecting sudden changes or movement

• Most vulnerable to flicker due to its high temporal resolution

• Responds strongly to rapid changes in luminance

• Sensitive to low spatial frequencies and high temporal frequencies

• Studies have shown M pathway neurons can follow flicker rates up to 60-80 Hz

Parvocellular (P) pathway:

• Processes fine detail and color information

• More sensitive to high spatial frequencies and lower temporal frequencies

• Important for form and object recognition

• Less sensitive to flicker compared to M pathway

• More responsive to steady-state stimuli

• Can still be affected by flicker, especially at lower frequencies

• Triggered by red-green opponency.

Koniocellular (K) pathway:

• Less well-understood compared to M and P pathways

• Involved in color processing, particularly blue-yellow distinctions

• May play a role in eye movement control and visual attention

• Less well-studied in terms of flicker sensitivity

• Some evidence suggests it may play a role in processing rapid color changes

Maybe one of the problems of KSF phosphor is mainly present when there is high frequency flickering, as instead of a simple brightness dip that affects the Magnocellular pathway, you would keep hammering the Parvocellular pathway with edge / no-edge / edge / no-edge. 15000 times pr second.

Remember that white on the display consists of RGB. So to avoid this you would need to remove either all red resulting in a cyan image, or remove both green and blue resulting in a pure red image. This can be done with Gamma Control if someone wants to experiment.

One thing to note is that if making blacks brighter or color shifted this effect could be significantly increased, as pure black doesn't generate any signal for yellow-blue opponency. One could also argue that newer screens getting better with less bleeding and overly blue backlight could trigger less of the different types of opponencies that the visual system uses to detect edges.

Say you want to create the maximum amount of opponency signals for text you would make blacks slightly gray and purple (blue and red), and you would make the whites greenish yellow. The luminance contrast is there in any case. Compared to a perfect screen with pure black and white you would have 3 opponency channels instead of 1. Not necessarily beneficial, but worth thinking about.

In any case I'm a strong advocate for experimenting with small color shifts the make screens feel better, and I think the differerent flicker rates of the colors for the MacBook display potentially could be the reason it messes up people.

@DisplaysShouldNotBeTVs

async How does the red modulation depth change when you disable IOMFB brightness compensation?

/Applications/BetterDisplay.app/Contents/MacOS/BetterDisplay set -namelike=built -framebufferBoolProperty=off -specifier=IOMFBBrightnessCompensationEnable

This command creates an immediate effect on M1 Air (not sure about mini-LED) where the backlight becomes noticeably more red and a "little bit more stable"

And when turning brightness compensation back on again, even though the backlight looks more blueish again, I immediately notice that there's still a red component but it's slightly flickery

So when brightness compensation is on, it's likely that it's done by flickering red subpixels in some way

Interestingly, a related experience is on a 2016 MacBook Pro, when in Boot Camp Windows 10 the backlight becomes more red and blue at 10% intervals, 100% is reddish 90% is blueish and so on. When in macOS the backlight temperature stays the same at all brightness levels. So this might be flickering red in order to compensate for the slight color temperature difference with different backlight levels.

BTW unlike the M1 Air, the 2016 13" Pro is PWM-free (but I still get some strain + a different set of issues with it)

I can notice a similar effect on iPhone 14 Pro. since that's OLED, it's not related to a backlight in that case, but I see the same type of flicker I notice on my M1 Air

In addition, if I use PWM-free screens for a while, the slight flickering of red I see in both devices becomes much more noticeable the next time I come back to them