When using an external monitor that supports 4K with a Mac, what resolution should I set it to?

I'm using a 27" 4K monitor with a Mac running Ventura 13.1. In the Displays Preferences, there are five choices, ranging from Larger Text to More Space. According to my monitor, the Mac always sends a 4K signal to it – no matter which of these modes the Mac is in.

Based on the "System Information" report, the choices are:

• UI Looks like: 1920 x 1080 / Resolution: 3840 x 2160 [Larger Text]
• UI Looks like: 2560 x 1440 / Resolution: 5120 x 2880
• UI Looks like: 3008 x 1692 / Resolution: 6016 x 3384
• UI Looks like: 3360 x 1890 / Resolution: 6720 x 3780
• UI Looks like: 3840 x 2160 / Resolution: 3840 x 2160 [More Space]

The first four modes are Retina modes. The "UI Looks like" is a guide for sizing. Retina-aware applications can draw onto an internal canvas in greater detail (see: "Resolution"). The last mode is non-Retina "native" mode.

I normally run my monitor one notch down from "Larger Text", in "looks like 2560 x 1440" mode. The "looks like 3008 x 1692" mode is also usable. I would not want to do much text work in "looks like 3360x1890" mode or in native "looks like 3840 x 2160" mode as the text is simply too small for comfortable reading.

In the "looks like 2560 x 1440" mode, the Mac is drawing onto a 5K canvas, but then downscaling that to display the contents at the actual 4K resolution of the screen.

Go to Displays in System Setting and select the external display. Click the "Advanced" button, turn on "Show resolutions as list", and click the "Done"

button. Turn on "Show all resolutions". For most resolutions you should now see two options:

1: low resolution - which runs the display at the listed low resolution for bigger text but lower image quality.

2: normail - which actually runs the display at higher than the listed resolution but increases in text size by generating more dots per character.

On a 27" 4K or 5K monitor, allowing applications to use the entire native resolution for extra workspace, and none of it for increased detail, makes text and objects uncomfortably small.

• There's no need to run a 5K monitor at native 5K resolution to get "the best image quality". You could run it at the Retina "like 2560 x 1440" setting.
• There's no need to run a 4K monitor at native 4K resolution to get "the best image quality". You could run it at the Retina "like 1920 x 1080" setting.

Now on a 27" 4K monitor, "like 1920 x 1080" text might be way too big, while "3840 x 2160" text might be way too small. So you'd run at one of the resolutions in the middle, say "like 2560 x 1440". The scaling might not be pixel-perfect, but the result might still be better than what you would get with an actual 27" 2560 x 1440 monitor.

liililil wrote:

I had the same thoughts regarding the resolution. I got a consistent response from Apple Support in Korea as well.

However, as depicted in the attached photo, both the Apple community and the Apple website suggest there's a difference between the actual and the configured resolution.

RE: "By default, your Mac automatically uses the best resolution for the display."

Most Macs that have Retina screens default to a "UI looks like" resolution that's exactly half of a display's native resolution, in each direction. E.g., a 5K Retina iMac that has a 5120 x 2880 pixel screen will default to the Retina "like 2560 x 1440" mode that results in Retina-aware applications drawing on a 5120 x 2880 pixel canvas. That takes full advantage of the 5K Retina screen – for extra detail and sharpness, not for cramming more and more text and objects onto the screen while the text and objects get tinier and tinier.

There are some exceptions to this rule.

A MacBook (Retina, 12-inch, Early 2015) has a LCD panel resolution of 2304 x 1440 pixels. But the default is not "looks like 1152 x 720" – it's "looks like 1280 x 800" (which, just coincidentally, matches the default for 13" MBPs that have 2560 x 1600 pixel screens and that can get to "looks like 1280 x 800" with exact 2x scaling).

After that, there were some MacBook Pros where Apple could have set the default to exact 2x scaling, but chose to set it to some option that resulted in more workspace, at the expense of smaller text.

Moreover, if adjusting the resolution truly impacts the display quality, I would expect to see a decline in quality when set to the lowest resolution, but I don’t notice any difference.

My main concern is this: When I set my Mac to a 4K resolution, the text and icons shrink to a nearly unusable size. If I use the default resolution setting, will it still provide 4K quality?

If you use any of the Retina settings, you will be making use of the monitor's 4K quality.

The Retina "like 1920 x 1080" setting will theoretically be more "pixel-perfect" than the others – as Retina-aware applications will be drawing on a 3840 x 2160 pixel "canvas" that perfectly matches the screen.

You will probably find, in practice, that you want to use one of the next two settings most of the time, even if the computer has to "munge pixels together" in the process of taking a high-resolution 5K or 6K canvas and putting the contents of that canvas onto the actual 3840 x 2160 screen.

If the "Advanced…" dialog on your machine gives you the option to, say, select a "low-resolution" 1920 x 1080 or 2560 x 1440 mode where Retina scaling is not involved, and you select such a mode, and your monitor accepts the signal, then you will not be making use of the monitor's 4K quality. The monitor will be upscaling from a low-resolution signal to a high-resolution screen. There you would be talking not just about loss from munging some high-resolution pixels together, but about loss from never having full detail in the first place.

Malcolm J. Rayfield wrote:

Go to Displays in System Setting and select the external display. Click the "Advanced" button, turn on "Show resolutions as list", and click the "Done"

button. Turn on "Show all resolutions". For most resolutions you should now see two options:

1: low resolution - which runs the display at the listed low resolution for bigger text but lower image quality.

2: normail - which actually runs the display at higher than the listed resolution but increases in text size by generating more dots per character.

Ventura 13.1 is not giving me the "Show resolutions as list" option for my display – just the 5 radio buttons. I am not sure if there is something I'm missing, if Apple is special-casing my display, or if they removed the feature.

At the end of the day you set to where you can comfortably read the screen. Everyone's vision is different.