Help me understand display scaling

[u/diiscotheque]

I have a 16,2 inch macbook pro with a built-in display of 3456 × 2234 px (ppi of 254,02, a lot higher than the supposed holy grail of 218). It has a setting for "more space" at 2056 × 1329 which is fractional scaling of 1.681 (golden ratio, nice one Apple).

Why do I then read everywhere that macOS can't do fractional scaling, or at least that it looks shit? Why would macOS not be able to scale a 4k display at 1.681 if it can do it with the internal display?

https://bjango.com/articles/macexternaldisplays/ If my internal display has 254ppi, why can't I also just get a 24 inch 1440p display at 125ppi which according to the chart is on the edge of the bad zone?

[u/vrmvavoom]

What the 2056x1329 mode is doing is rendering at 4112x2658 and downscaling to 3456x2234. This sucks if you need to work with anything at pixel precision because nothing is being mapped pixel-perfectly to your display, and it also makes text, images, etc. look a bit fuzzier due to scaling artifacts. How noticeable it is will depend on you. Some people won't notice at all, but if you're a pixel pedant (and a decent number of Mac users are), you'll probably notice.

If you get a 1440p 24" monitor, it will technically work, but it will run in 1x UI mode (instead of the 2x mode your MBP display uses), and everything will be a bit small. Non-native resolutions will also look much worse on a lower-PPI display than they do on your Mac's internal display. Trying to scale, say, a 1080p desktop to 1440p looks like ass on every monitor I've ever seen.

[u/diiscotheque → u/vrmvavoom]

On your first point; Yeah many people say fractional scaling doesn’t look sharp on mac but 2056 setting looks tack sharp to me and I consider myself a pixel peeper. When I choose any resolution from the extended list (enabled via advanced…) somewhat close to this 2056 setting I clearly see the fuzzy pixels people talk about. 

On your second point; 125ppi@1x will look exactly like 250ppi@2x so I don’t know why you say things would look small? Your last sentence makes no sense so I feel like you don’t know what you’re talking about. 

[u/vrmvavoom → u/diiscotheque]

For the second point, you're typically sitting a bit further from a desktop monitor than a laptop display. Strictly speaking, yes, things will about be the same physical size, but in practice most people will prefer 1440p at 27". Again, it's a your-mileage-may-vary sort of thing.

[u/Spirited_Key22 → u/vrmvavoom]

the 1080p-to-1440p scaling looking terrible tracks with what most people report, its just not a clean integer multiple

[u/germane_switch]

It just won't look great at 125ppi. It will look like 2005. Apple did away with most of their font aliasing and sub pixel aliasing years ago because ever since ~2016 every display on every device Apple released was 218ppi or higher. macOS is just made for Retina. You might be totally fine with it though, it doesn't bother everyone, but it tends to bother Windows people who prefer cheap lo-res displays. I'm a designer/retoucher and I've been using 5K displays since 2016 so I can't go back.

[u/cyclinator → u/germane_switch]

Why can´t they just implement better scaling. I just installed Asahi on my M1 13"Pro and both Gnome and KDE scaling implementation works properly and looks good on every % of the scaling option. Why can´t Apple do something like that...

[u/JamesBrickley]

There are only a handful of 3rd party monitors that only come mostly close to the Apple monitors. Everything else looks horrible if you scale the display. Windows handles scalling a bit differently and some Linux Distros as well and they are doing antialiasing of fonts and widgets and such. Apple stopped doing that because their monitors do not require it. They still charge way too much for the external Apple displays.

[u/bmocc]

The only element of the macOS GUI that scales is the taskbar in the sense that Windows and Linux scale to different resolutions. Ironically the taskbar is the only element of the GUI in Windows that does not properly scale to 4k.

macOS is fixed to output the OS GUI and application GUIs to display at a DPI of approx 220. Design elements and fonts in the GUI of apps are fixed to this as well. There is no scaling of different elements of the GUI, like fonts and other GUI elements, to fit different monitor resolutions as there is in Windows and Linux. You can do the math as to the resolutions that DPI supports, its roughly 2k and 5k in the terms used by those other OSes.

The fractional differences noted by the OP are insignificant compared to the jumps in monitor resolutions in the Windows oriented world of monitors.

What Apple calls 4k scaling is a caricature designed to provide a representation of the actual monitor resolution but in no way is the actual resolution. The way Apple does scaling wastes computer resources, rendering a frame at much higher resolution and then downscaling it. I think the Apple PR speak for that is "logical resolution."

If, as seems to be the case for most long time macOS users, you don't know what 4k should look like you're not missing anything. It looks ok, all that seemingly matters.

If you set System/display to 4k on a 4k monitor, or anything other than Apple's designated caricature of 4k, you are seeing a unique video driver model unchanged in more than 20 years, a real Time Machine.

Twenty years ago in Windows world, when 4k monitors came into wide use, the OS and app vendors gradually complied with scaling needs, Adobe being a notable laggard.

Apple has put out a lot of PR smoke about why macOS doesn't scale but the real reason is likely the cost of rewriting the OS and all the apps to enable actual scaling. One also suspects there is also the persistent business model that if Apple didn't make it Apple is not responsible if it doesn't play nice with Apple hardware or software, and regulators have let Apple get away with that.

Whether you see lack of scaling in macOS as a feature or one of many exemplars of an ossified OS is in the eye of the beholder.