These issues keep coming up in questions about alternative displays, especially now that the option of a “cheap” 5k iMac has disappeared.
Apple presents screen modes like “1020x1080” under the heading “Resolution” in the Display Settings box - but on a 4k, 5k or “Retina” display these really aren’t the resolution you see on the screen. Seeing comments like “I’m running my display at 1280x1080” could be misleading - even if the poster knows what they are talking about.
To keep things simple, for the purposes of this post:
“4k” is shorthand for “‘4k’ UHD 3840x2160” - most issues about 4k are also relevant to 3840x2560 (3:2) and 5120x2160 (ultra wide) screens.
“5k” is shorthand for 5120x2880 (and not 5k ultra-wide which is usually something like 5120x2160 & raises the same issues as 4k)
“UI” size refers to the physical (I.e. take a ruler to the screen/count the pixels) size of system fonts, icons, buttons, menus, dialogues etc. and may also affect the meaning of things like “100%” scale in some apps.
(All of which can be nit-picked of course, but I’m trying to keep this shorter than War and Peace)
Unless stated otherwise, I’m talking about default modes and the initial, limited choice of “Scaled” modes. We’re not option-clicking, not running SwitchResX etc. to get at “hidden” modes.
I’ll put the Apple mode names in quotes (“1920x1080”) as a reminder that they don’t mean what they appear to mean.
====
1. You’re not “wasting” your 4k monitor by running in “1920x1080” mode.
The mode in displays settings describe the user interface size.
The most obvious effect of.changing the display mode on a 4k/5k/Retina is just that the MacOS user interface (UI) elements - system fonts, menus, icons, buttons, scroll bars etc. appear larger or smaller.
It’s a bit more complex than that - and some settings do give better image quality than others - but a 4k display is always running at 4k and giving more detail than you’d get on a regular 1920x1080 (1080p or “full HD”) display.
(Stop reading here if you’re happy with a slightly dumbed-down, TL
NR, soundbite answer to everything).
Apple’s names for the modes actually just describe the UI size in terms of old, low res displays - so “2560x1440” just means that the system fonts, menus etc. on a 27” display are the same size as they would have been on an old-school 27” iMac or Cinema/TB display. In older OS versions this used to be described as “looks like 2560x1440”.
2. “1920x1080” or “3840x2160” both give “optimum” image quality for s 4k screen
What Apple calls “1920x1080” is still exactly 3840 pixels by 2160 - full 4k - but with the MacOS UI displayed at twice the size [0]. Also known as “HiDPI”, “2x” or “Retina” mode. The content in your application will be displayed at full 4k detail (but you may want to adjust the application’s zoom setting or the font size in a code editor to take advantage of it) [1].
(This is similar to the situation on 5k displays where the default mode - everybody’s “gold standard” - is actually described as “2560x1440” i.e. 5120x2880 with a 2x user interface).
Some people find that this makes the menu, dock, dialogue boxes etc. take up too much space or look too big and clunky on a 27” screen.
Choosing “3840x2160” doesn’t change the screen resolution, but doesn’t use the double-sized user interface. Most people find this too small and fiddly to be comfortable on a 27” or smaller display. That’s why it isn’t the default. Any content rendered by modern applications should have the same level of detail as in “1920x1080” (but you may have to adjust the zoom/font size within the App).
Confusingly, the Display Settings dialogue bunches these under “scaled” modes - but they are not the dreaded “fractionally scaled” modes you may have heard complaints about.
Apart from the UI size, the level of detail displayed is identical. The issue is with the physical UI size: on a 27” display, “1920x1080” looks too big, “3840x2160” looks too small. For many people the “Goldilocks zone” would be somewhere in between.
…but please remember, your eyesight may vary - and it also depends on what Apps you use, whether you work in full screen, or whether you have a multi-screen setup that lets you move tool palettes to a second screen etc. Be skeptical of anybody who claims either of these modes is “unusable”.
Illustration: here are 2 screen photographs of a 4k screen showing an Affinity Designer bitmap image with zoom set to “pixel size”. The two ‘grids’ are alternating black and white stripes exactly 1 pixel apart. The camera was at the same distance from the screen & zoom setting for both. First image is in what Apple describes as “1920x1280” [4], second is “3840x2560” mode. You can see that the UI text/icons shrink, but the individual pixels in the graphics are the same physical size and resolution.
NB: the “a” and the 2 squares, together, are about 1” wide on screen. From my normal viewing distance the two squares are just on the verge of appearing to merge into solid grey..
3. “2560x1440” and other “fractionally scaled” modes.
On a 4k display, what effectively happens in “2560x1440” mode is that everything is rendered to an internal “virtual” screen at 5k - I.e. 5120x2880 with a 2x user interface (convince yourself by taking a screen grab then loading it into a photo editor) which is then “downsampled” to 4k and displayed on your screen.
The first effect of this is that the UI (when seen on a 27” screen) is the same size as on a classic “2560x1440” iMac - which is widely regarded as “just right” (YMMV - it’s actually pretty small).
The downsides are:
(a) It places an extra load on the GPU, which is why a “using scaled modes may affect performance, This may be an issue on a machine with a weak GPU or limited VRAM - such as Intel integrated graphics - but a recent Intel machine with a discreet GPU, a M1 Pro or Max - and probably an M1 (unless you’re running out of RAM for other reasons) - should eat it for breakfast. Edit: there's some evidence that it can impact 3d workloads on regular M1 - which is probably pushing the envelope for M1 machines anyway (and remember that from the App's perspective it is running at 5k which is quite a big ask for 3D).
(b) One pixel on the real screen does not map to a whole number of pixels on the virtual screen. This results in a slight “soft focussed” effect, and makes moving an object 1 pixel at a time slightly imprecise, This really is a case of “your mileage may vary” - in most cases you won’t notice a difference from 20” away, but if you’re trying to do “pixel accurate” work at 1:1 scale by leaning in close or leveraging your better-than-average eyesight it will be a problem, unless you zoom in to 200%+ scale. However, remember, that it only takes a few seconds to change modes if you ever need 1:1 pixel rendering & the vast majority of creative applications have fully zoomable content.
Note that some MacBook models default to fractionally scaled modes. They’re not evil.
The other “intermediate” modes (3008x1692, 3360x1890) work in a similar way, but offer progressively smaller UI sizes that might be useful on larger displays.
I’m thinking of the best way to illustrate this - the 1 pixel stripes from the other images really are the worst possible case and look awful, but I’ll be honest and post what it looked like at “2560x1707” (the 3:2 equivalent of “2560x1440”) - note that in this case, Affinity thinks its on a 5k display so it gets the “Pixel Size” wrong and the image is physically smaller than before. Note the cm/mm scale - this image is tiny.and you probably wouldn’t see the issue from 20” away. Also note that while the 1px stripes have gone, the ‘a’ is still fairly smooth. But if working at this level (without zooming in) is your day job you probably don't want to use fractionally scaled modes.
4. 4k is not 5k
5k is higher resolution than 4k. 5k is a “sweet spot” resolution for MacOS - for people with average eyesight. It will look better.
On the other hand, 5k displays are 2-3 times the price of a quite decent 4k display and there’s only really two 5k displays readily available on the market (and that’s stretching the meaning of “readily available”!) so you can afford a pretty good multi-4k-display setup for the cost of a 5k. There’s also a wide choice of extra-large, extra-wide displays, cheap OLED TVs (for HDR on a budget) to choose from. For many people, a 4k display is a very good compromise.
5. Retina
Retina display” is an Apple marketing term - but the idea is based on the definition of “20/20” or “6/6” vision (https://en.wikipedia.org/wiki/Visual_acuity#Definition) which boils down to being able to “separate contours” 1.75mm apart at a distance of 6m. That corresponds to an angular resolution of 1 arc minute (0.0003 radians) as the limit of human vision (also a common rule of thumb in physics/optics/astronomy).
If you make a shedload of reasonable - if debatable - assumptions, not least that being able to “separate contours” => being able to distinguish individual pixels[2] - that (0.0003 radians) corresponds to the ‘300ppi at 12”’ ( (1/300)//12 = 0.000277) threshold used by Apple. Note, that it depends on distance - which is why there are different “retina” PPI standards for different types of device. 12” assumes that you’re going to hold your iPhone like a book.
If you expand that to a desktop display, a 27” 4k monitor has 163 PPI giving a retina distance of 21” - which is pretty much how far I sit from a desktop display. So a 27” 4k display is retina.
…but let’s be realistic about that: the definition isn’t unscientific but it contains a lot of simplifying assumptions: and 20/20 is normal vision - not perfect vision. So it’s certainly not saying that you, personally, can’t see the difference between 4k and 5k - my vision (maybe except when I’ve just got new glasses) isn’t even 20/20 and I can see that 5k looks “crisper”[3]. Also, if you go to a larger 4k display - e.g. 32” - the “retina” distance gets longer. Some people will move the display further away to compensate, others won’t…
I think the best thing to say is that once you get past 4k@27” you’ll see diminishing returns from improving the PPI, and that many people won’t notice pixel-sized artefacts (such as the effect of fractional scaling) unless they lean in to the display.
(edit) 6. Is a regular 1440p (or other low res) display an option?
This post assumes you want/need a high-def (4k, 5k or better) display. Nothing else will give quite the same level of sharpness - but there are other measures of quality and practicality that might make a regular 2560x1440 (2k) display the best price/performance compromise for your particular workflow. E.g. particular colour gamut or calibration features for photo work, perhaps you spend most of your time working at "actual pixels" zoom, or maybe your Mac struggles to render 3D at 4k (scaling or none). There are several comments about this below. Otherwise, this is "beyond the scope of this post" and just point out that a few short years ago we were all drooling over Apple Cinema/Thunderbolt displays and their super-high 1440p resolution, before we were all seduced by the luxury of "cheap" 5k iMacs...
====
Hope this is useful.
====
[0] I.e. twice the horizontal and vertical size, or 4x the number of pixels, - so 8x8 becomes 16x16.
[1] A few, old/sloppy apps may not support “retina” mode, and will appear fuzzy, but that is increasingly rare. The majority of current MacOS software will include images for high res icons and scale things properly,
[2] More realistically, it’s being able to see a 1 pixel gap between two lines - which seems like a fair approximate correspondence with being able to notice 1 pixel ‘jaggies’ on text etc.
[3] …although Apple panels also have very good optical coatings and high brightness that gives nice, high contrast text - which helps.
[4] Note - this was actually a Mateview with a 28.3” 3:2 screen hence 1920x1080/3840x2560 - but the width of the screen and pixel density is exactly the same as a 27” 3840x2160 screen - it’s basically a 3840x2160 screen with 400 extra vertical pixels glued on the bottom.
Apple presents screen modes like “1020x1080” under the heading “Resolution” in the Display Settings box - but on a 4k, 5k or “Retina” display these really aren’t the resolution you see on the screen. Seeing comments like “I’m running my display at 1280x1080” could be misleading - even if the poster knows what they are talking about.
To keep things simple, for the purposes of this post:
“4k” is shorthand for “‘4k’ UHD 3840x2160” - most issues about 4k are also relevant to 3840x2560 (3:2) and 5120x2160 (ultra wide) screens.
“5k” is shorthand for 5120x2880 (and not 5k ultra-wide which is usually something like 5120x2160 & raises the same issues as 4k)
“UI” size refers to the physical (I.e. take a ruler to the screen/count the pixels) size of system fonts, icons, buttons, menus, dialogues etc. and may also affect the meaning of things like “100%” scale in some apps.
(All of which can be nit-picked of course, but I’m trying to keep this shorter than War and Peace)
Unless stated otherwise, I’m talking about default modes and the initial, limited choice of “Scaled” modes. We’re not option-clicking, not running SwitchResX etc. to get at “hidden” modes.
I’ll put the Apple mode names in quotes (“1920x1080”) as a reminder that they don’t mean what they appear to mean.
====
1. You’re not “wasting” your 4k monitor by running in “1920x1080” mode.
The mode in displays settings describe the user interface size.
The most obvious effect of.changing the display mode on a 4k/5k/Retina is just that the MacOS user interface (UI) elements - system fonts, menus, icons, buttons, scroll bars etc. appear larger or smaller.
It’s a bit more complex than that - and some settings do give better image quality than others - but a 4k display is always running at 4k and giving more detail than you’d get on a regular 1920x1080 (1080p or “full HD”) display.
(Stop reading here if you’re happy with a slightly dumbed-down, TL
NR, soundbite answer to everything).Apple’s names for the modes actually just describe the UI size in terms of old, low res displays - so “2560x1440” just means that the system fonts, menus etc. on a 27” display are the same size as they would have been on an old-school 27” iMac or Cinema/TB display. In older OS versions this used to be described as “looks like 2560x1440”.
2. “1920x1080” or “3840x2160” both give “optimum” image quality for s 4k screen
What Apple calls “1920x1080” is still exactly 3840 pixels by 2160 - full 4k - but with the MacOS UI displayed at twice the size [0]. Also known as “HiDPI”, “2x” or “Retina” mode. The content in your application will be displayed at full 4k detail (but you may want to adjust the application’s zoom setting or the font size in a code editor to take advantage of it) [1].
(This is similar to the situation on 5k displays where the default mode - everybody’s “gold standard” - is actually described as “2560x1440” i.e. 5120x2880 with a 2x user interface).
Some people find that this makes the menu, dock, dialogue boxes etc. take up too much space or look too big and clunky on a 27” screen.
Choosing “3840x2160” doesn’t change the screen resolution, but doesn’t use the double-sized user interface. Most people find this too small and fiddly to be comfortable on a 27” or smaller display. That’s why it isn’t the default. Any content rendered by modern applications should have the same level of detail as in “1920x1080” (but you may have to adjust the zoom/font size within the App).
Confusingly, the Display Settings dialogue bunches these under “scaled” modes - but they are not the dreaded “fractionally scaled” modes you may have heard complaints about.
Apart from the UI size, the level of detail displayed is identical. The issue is with the physical UI size: on a 27” display, “1920x1080” looks too big, “3840x2160” looks too small. For many people the “Goldilocks zone” would be somewhere in between.
…but please remember, your eyesight may vary - and it also depends on what Apps you use, whether you work in full screen, or whether you have a multi-screen setup that lets you move tool palettes to a second screen etc. Be skeptical of anybody who claims either of these modes is “unusable”.
Illustration: here are 2 screen photographs of a 4k screen showing an Affinity Designer bitmap image with zoom set to “pixel size”. The two ‘grids’ are alternating black and white stripes exactly 1 pixel apart. The camera was at the same distance from the screen & zoom setting for both. First image is in what Apple describes as “1920x1280” [4], second is “3840x2560” mode. You can see that the UI text/icons shrink, but the individual pixels in the graphics are the same physical size and resolution.
NB: the “a” and the 2 squares, together, are about 1” wide on screen. From my normal viewing distance the two squares are just on the verge of appearing to merge into solid grey..
3. “2560x1440” and other “fractionally scaled” modes.
On a 4k display, what effectively happens in “2560x1440” mode is that everything is rendered to an internal “virtual” screen at 5k - I.e. 5120x2880 with a 2x user interface (convince yourself by taking a screen grab then loading it into a photo editor) which is then “downsampled” to 4k and displayed on your screen.
The first effect of this is that the UI (when seen on a 27” screen) is the same size as on a classic “2560x1440” iMac - which is widely regarded as “just right” (YMMV - it’s actually pretty small).
The downsides are:
(a) It places an extra load on the GPU, which is why a “using scaled modes may affect performance, This may be an issue on a machine with a weak GPU or limited VRAM - such as Intel integrated graphics - but a recent Intel machine with a discreet GPU, a M1 Pro or Max - and probably an M1 (unless you’re running out of RAM for other reasons) - should eat it for breakfast. Edit: there's some evidence that it can impact 3d workloads on regular M1 - which is probably pushing the envelope for M1 machines anyway (and remember that from the App's perspective it is running at 5k which is quite a big ask for 3D).
(b) One pixel on the real screen does not map to a whole number of pixels on the virtual screen. This results in a slight “soft focussed” effect, and makes moving an object 1 pixel at a time slightly imprecise, This really is a case of “your mileage may vary” - in most cases you won’t notice a difference from 20” away, but if you’re trying to do “pixel accurate” work at 1:1 scale by leaning in close or leveraging your better-than-average eyesight it will be a problem, unless you zoom in to 200%+ scale. However, remember, that it only takes a few seconds to change modes if you ever need 1:1 pixel rendering & the vast majority of creative applications have fully zoomable content.
Note that some MacBook models default to fractionally scaled modes. They’re not evil.
The other “intermediate” modes (3008x1692, 3360x1890) work in a similar way, but offer progressively smaller UI sizes that might be useful on larger displays.
I’m thinking of the best way to illustrate this - the 1 pixel stripes from the other images really are the worst possible case and look awful, but I’ll be honest and post what it looked like at “2560x1707” (the 3:2 equivalent of “2560x1440”) - note that in this case, Affinity thinks its on a 5k display so it gets the “Pixel Size” wrong and the image is physically smaller than before. Note the cm/mm scale - this image is tiny.and you probably wouldn’t see the issue from 20” away. Also note that while the 1px stripes have gone, the ‘a’ is still fairly smooth. But if working at this level (without zooming in) is your day job you probably don't want to use fractionally scaled modes.
4. 4k is not 5k
5k is higher resolution than 4k. 5k is a “sweet spot” resolution for MacOS - for people with average eyesight. It will look better.
On the other hand, 5k displays are 2-3 times the price of a quite decent 4k display and there’s only really two 5k displays readily available on the market (and that’s stretching the meaning of “readily available”!) so you can afford a pretty good multi-4k-display setup for the cost of a 5k. There’s also a wide choice of extra-large, extra-wide displays, cheap OLED TVs (for HDR on a budget) to choose from. For many people, a 4k display is a very good compromise.
5. Retina
Retina display” is an Apple marketing term - but the idea is based on the definition of “20/20” or “6/6” vision (https://en.wikipedia.org/wiki/Visual_acuity#Definition) which boils down to being able to “separate contours” 1.75mm apart at a distance of 6m. That corresponds to an angular resolution of 1 arc minute (0.0003 radians) as the limit of human vision (also a common rule of thumb in physics/optics/astronomy).
If you make a shedload of reasonable - if debatable - assumptions, not least that being able to “separate contours” => being able to distinguish individual pixels[2] - that (0.0003 radians) corresponds to the ‘300ppi at 12”’ ( (1/300)//12 = 0.000277) threshold used by Apple. Note, that it depends on distance - which is why there are different “retina” PPI standards for different types of device. 12” assumes that you’re going to hold your iPhone like a book.
If you expand that to a desktop display, a 27” 4k monitor has 163 PPI giving a retina distance of 21” - which is pretty much how far I sit from a desktop display. So a 27” 4k display is retina.
…but let’s be realistic about that: the definition isn’t unscientific but it contains a lot of simplifying assumptions: and 20/20 is normal vision - not perfect vision. So it’s certainly not saying that you, personally, can’t see the difference between 4k and 5k - my vision (maybe except when I’ve just got new glasses) isn’t even 20/20 and I can see that 5k looks “crisper”[3]. Also, if you go to a larger 4k display - e.g. 32” - the “retina” distance gets longer. Some people will move the display further away to compensate, others won’t…
I think the best thing to say is that once you get past 4k@27” you’ll see diminishing returns from improving the PPI, and that many people won’t notice pixel-sized artefacts (such as the effect of fractional scaling) unless they lean in to the display.
(edit) 6. Is a regular 1440p (or other low res) display an option?
This post assumes you want/need a high-def (4k, 5k or better) display. Nothing else will give quite the same level of sharpness - but there are other measures of quality and practicality that might make a regular 2560x1440 (2k) display the best price/performance compromise for your particular workflow. E.g. particular colour gamut or calibration features for photo work, perhaps you spend most of your time working at "actual pixels" zoom, or maybe your Mac struggles to render 3D at 4k (scaling or none). There are several comments about this below. Otherwise, this is "beyond the scope of this post" and just point out that a few short years ago we were all drooling over Apple Cinema/Thunderbolt displays and their super-high 1440p resolution, before we were all seduced by the luxury of "cheap" 5k iMacs...
====
Hope this is useful.
====
[0] I.e. twice the horizontal and vertical size, or 4x the number of pixels, - so 8x8 becomes 16x16.
[1] A few, old/sloppy apps may not support “retina” mode, and will appear fuzzy, but that is increasingly rare. The majority of current MacOS software will include images for high res icons and scale things properly,
[2] More realistically, it’s being able to see a 1 pixel gap between two lines - which seems like a fair approximate correspondence with being able to notice 1 pixel ‘jaggies’ on text etc.
[3] …although Apple panels also have very good optical coatings and high brightness that gives nice, high contrast text - which helps.
[4] Note - this was actually a Mateview with a 28.3” 3:2 screen hence 1920x1080/3840x2560 - but the width of the screen and pixel density is exactly the same as a 27” 3840x2160 screen - it’s basically a 3840x2160 screen with 400 extra vertical pixels glued on the bottom.
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