M1 vs Intel macOS scaling differences

[KrisCris]

I am using DELL U2518D, a 2560*1440 display. Configured HIDPI using BetterDisplay, and tried both ways in the readme.

However,

There are some weird white (or black) outlines on the text edges⬆️, which is not the case on my old mac mini⬇️ (it uses one-key-hidpi):

The white border makes the text looks very blurry and weird, I don't know why would this happen.

[waydabber]

This is not a BetterDisplay or one-key-hidpi issue, the scaling engine produces a somewhat different result in M1 vs Intel. The effect is super pronounced (and imho annoying) if you invert the screen but should not be that noticeable for normal use. Supposedly the change in scaling is to improve sharpness.

[KrisCris]

I will post the result once I got time today or maybe tomorrow! I don't know why apple would change the scaling, looks fuzzy even on my internal display if I use the "more space" option.

[waydabber]

I am not sure, I was not noticing it much unless I inverted the screen (I had to do that working with some some old full screen app that does not support dark mode) and I was appalled as the effect become much more pronounced.

[KrisCris]

So I just tested that font smoothing... I don't know, can't see any difference IMO, doubt if it's still working.

[waydabber]

Yes, my conclusion exactly. It might work on Intel or might have worked on Big Sur, but I could not pinpoint any difference last time I was testing it.

[KrisCris]

Yeah, actually take a second eye on the HIDPI, still fuzzy but acceptable! Maybe I just need to let my eyes get used to it lol

[tvules]

Hi, still no solution to fix it? I have the same problem.

I'm using a 1440p display with MBP M1 and downscaling to 2048x1152. I noticed that 1280x720 looks perfect but the UI is too big to use.

[tvules]

It's not monitor dependent, I've tried on another 1080p monitor and on my 4k TV. Only x2 downscaling from native resolution has no problem.

However, with this smoothing level, the text looks better, but the problem remains.

defaults -currentHost write -g AppleFontSmoothing -int 0

[matthewlloyd]

It turns out the new 15" M2 MBA has this issue on the internal display at the default scaling. Something felt off to my eyes, and I didn't figure out what the issue was until I took a magnifying glass to the screen.

I couldn't find anything in defaults that might be related, but really hope there is some way to turn this off. It makes text look fuzzy and creates artificial edges in images and around icons.

The workaround for the MBA is to set the scaled resolution to an exact 2:1 ratio of the native resolution 2880x1864, i.e. 1440x932. The sharpening filter seems only to be enabled when the scaled resolution does not perfectly divide the native resolution. Unfortunately for the MBA, doing so reduces the effective screen real estate to less than the 14" MBP, which has a higher native resolution and uses a 2:1 ratio by default.

[matthewlloyd]

I just discovered an interesting workaround on the MBP's with XDR displays, which normally show this same sharpening artifact at non-integer ratio resolutions: run TotalXDR, but leave the high brightness mode turned off. As long as it is running, there is very little (no?) sharpening artifact visible, even at regular brightness. I haven't tried this with BetterDisplay but it probably works there too, assuming it uses the same method to unlock the full XDR brightness of 1000 nits as TotalXDR. Given the method is to play with the color space, I'd guess the sharpening artifact with the Apple silicon scaling engine probably has something to do with that, and it may be possible for apps like BetterDisplay to disable it and not just on devices with XDR displays.

[waydabber]

Checked it, uses a similar method but without any way to adjust the intensity + it is hard calibrated to work only with XDR displays.

(edit: removed grumpy comment ;))

[waydabber]

With BetterDisplay you can slightly change the colortable for any display if you want + you can turn off resetting color table when no alterations are present after brightness upscaling for HDR and XDR displays here:

[matthewlloyd]

With BetterDisplay you can slightly change the colortable for any display if you want + you can turn off resetting color table when no alterations are present after brightness upscaling for HDR and XDR displays here:

Thank you for the information, what a powerful and super configurable program you have created here! I tried playing with the colortable on an Air with a non-XDR display - playing with the brightness and contrast can make the artifact weaker or stronger, suggesting it appears in the rendering pipeline before the color space mapping is done, but there didn't seem to be a setting that made it disappear without also compromising color accuracy somehow.

[waydabber]

So your goal is to replicate the effect on a non-XDR display? I am not sure colortable manipluation actually has an effect on image sharpening or maybe it has but only when the display is in EDR mode (for XDR/Apple displays or maybe third party HDR displays), that's why it has its effect with upscaling enabled?

[matthewlloyd]

Yes, my Air 15's display would be better if... I could disable the sharpening somehow. The colortable manipulation doesn't turn off the sharpening in non-EDR mode, it's just a way to hide the artifacts by pushing them off the black/white clip points. I think you're right about the different effect in EDR mode, which makes me wonder whether fooling the OS into thinking the non-XDR display does support EDR and putting it in "EDR mode" would disable the sharpening, since writing to Apple is unlikely to work (haha).

[RyotaMono]

Finally, at least I found a workaround. The source is acutally from the LONG discussion post from LEDStain.

In short (though highly recommend the reader to go to the post to see the original author's work),
(1) use the natural LoDPI for your monitor. e.g (2560x1440 in LoDPI for your 2K monitor) ;
(2) create a virutal display, with the same aspect ratio. Set this virtual display to the scaled resolution in HiDPI that you normally would applied to your phscial monitor.
(3) Instead of Mirror the display, Stream the Virtual Display (in the dropdown functions at menu bar) to your Physcial Display. Experimented with the Integer Scaling if 2x/3x.

Now it is EXACTLY like what I used a intel mac to connect to the physcial monitor!! You can even toggle the HiDPI option for your physical monitor in menu to actually view the difference before and after the "sharpen effect from M-series chips" - obvious and annoying.

I still want to have a more direct solution, probably at driver/system layer. Because beside this streaming setup, you also need to spend some time to configure the Display Groups, arrangement, Refresh Rate (my m4 pro seems cannot stream with more than 130hz), Display Spaces etc.

The difference seems can be somewhat visualized using the screencapture, just for illustration purpose.
The original HiDPI scaling way:

The streaming from virtual display and LoDPI for physical monitor way: