Conditional hybrid Retina display resolution

March 24, 2023 10:14 AM

Enabling Retina display scaling settings on, say, 5K monitors (5120 x 2880) reduces that display's resolution to 2560 x 1440 pixels. Is the resolution change applied to everything the operating system renders on screen, or can it be set to conditionally render, say, very high-resolution images (like dense heatmaps or medical images) within a web browser or image viewer, using non-Retina 1:1 scaling? (More inside...)

I suspect that part of the answer is that everything is currently rendered in doubled form — mainly, my question is whether Retina-doubling could be partially disabled for content within apps on a conditional basis, especially a web browser presenting such images, even if that might currently be an experimental feature. Especially appreciate answers from people familiar with the operating system (macOS) or web browsers (Chrome/Firefox/Safari) on a professional or industry level.

posted by They sucked his brains out! to Computers & Internet (7 answers total)

Is the idea that you want bigger windows, controls, fonts, and stuff like that, but you'd like high resolution content to display at a high resolution? You would think Apple would have a way to decouple interface component size from screen resolution, but I've never heard of that.
posted by Winnie the Proust at 10:45 AM on March 24, 2023

The scaling setting appears to be universal, and not per-app: there's no way for me to specify resolutions on a per-app basis. The system preferences are decidedly global.

Your assertion of "doubling" seems incomplete. My Retina mac and 4K monitor offers me scales of 1920x1080, 2560x1440, 3008x1692, 3360x1890, and 3840x2160 on a monitor that offers me a native 3840x2160, and I can confirm that identical characters in small fonts look different depending on where on the screen they appear on the screen when I am in a non-integer based scaling.
posted by the Real Dan at 10:51 AM on March 24, 2023

Response by poster: Your assertion of "doubling" seems incomplete.

I believe doubling to be the default setting for Retina displays, though you are correct that other custom scaling options are usually available.
posted by They sucked his brains out! at 11:07 AM on March 24, 2023

Changing the scaling of the screen between "larger text" and "more space" just changes the size of the UI elements. MacOS always uses all available hardware pixels for graphics unless you override the output resolution. There is a lot of internal fuckery going on, but in general apps (including Safari web browser) will display on the screen at least as much detail as the hardware can handle. Your mileage may vary depending on app. (More technically: an application can know the hardware vs. UI coordinate scaling in effect, and for Image data types should send at least as many pixels as the hardware can use. For some devices this is up to 3x the effective UI resolution.)
posted by seanmpuckett at 11:21 AM on March 24, 2023 [3 favorites]

Apple Insider has a decent explanation of macOS display scaling. If your Mac is connected to an external display with a resolution of 218ppi (matching the internal standard for a "Retina" display) then the OS will actually render what you're seeing at the full 218ppi the display supports. Text is rendered at higher resolution so that it looks sharper. Photo or video media, on the other hand, will display at its full native resolution, not a scaled resolution. If you watch or edit 4K video on a 5K iMac with display settings at "default for display," you see every pixel and not something resampled.

If you use display scaling to select some other option than "default for display" then the OS natively scales everything (including media) up to an even multiple of the target resolution, and then scales down from that for display. This results in a sharper display at the target resolution, but can still introduce scaling artifacts (arguably fewer obvious artifacts than if the OS scaled directly to the target resolution). The Apple Insider link has some simple illustrations of how that can result in moiré; Bjango has an in-depth piece with more examples.
posted by fedward at 11:23 AM on March 24, 2023 [2 favorites]

Not entirely sure if this works for you. I work a lot with projectors and high/custom resolutions. SwitchRes is invaluable for allowing non standard resolutions (or what the mac wants to allow you.)
posted by multivalent at 12:43 PM on March 24, 2023 [1 favorite]

And to follow (sorry for the double post) on it also seems to support custom resolutions for different apps, so maybe this is the way! I've never used it in that way (my use case has only to be set multiple projectors in an array) But there's a free trial, and their customer support is very good. So could well be worth a try
posted by multivalent at 12:53 PM on March 24, 2023