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schmorf

macrumors newbie
Original poster
Apr 22, 2020
9
8
Hi!

While researching about 4K monitors for my MacBook Air 2020 I found out that many mac users experience performance issues when applying scaling. More precisely when scaling not to the native 4K resolution or 1080p but between the "more space" and "larger text". Somewhere in the middle there is the scaling option "Looks like 1440p" which would be the factor I would use. But because of the way scaling works in MacOS it seems to be pretty inefficient when the factor is not 1:1 or 1:2. That is why Apple produced a 5K display instead of a 4K display.

So can anybody confirm this as well, or is this problem overblown, especially when using hardware from 2020?

On paper this should be a huge problem for anyone who wants to use an external 4K monitor since native resolution without scaling is unusable small and 1080p is way too big. But it seems that except for a couple of threads and videos nobody talks about this issue or cares. That's why I wanted to know if it actually is still a thing before buying a 4K monitor.

I wanted to get the Dell Ultrasharp U2720Q 4K, but as an alternative I would purchase the U2719DC QHD.


Good explanation of the problem:
https://bjango.com/articles/macexternaldisplays/

Some references where people experience performance drops:
https://forums.macrumors.com/threads/anybody-running-27-4k-monitors-in-1440p-scaled-mode.2026551/
https://forums.macrumors.com/thread...92-resolution-on-an-external-display.2102991/
https://apple.stackexchange.com/que...tor-and-performance-issues-with-mbp-late-2015

YouTube references:
 
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Fishrrman

macrumors Penryn
Feb 20, 2009
28,327
12,451
IF you're going to use a display that "looks like" 1440p all the time, why not consider a 32" 1440p display that will run at that resolution (2550x1440) in native mode -- and thus, put minimal strain on the GPU to begin with?

Dot pitch is a very usable .277mm @ 1440p on 32"...
 

schmorf

macrumors newbie
Original poster
Apr 22, 2020
9
8
IF you're going to use a display that "looks like" 1440p all the time, why not consider a 32" 1440p display that will run at that resolution (2550x1440) in native mode -- and thus, put minimal strain on the GPU to begin with?

Dot pitch is a very usable .277mm @ 1440p on 32"...
Because I want a higher pixel density, and scaled 4K 1440p looks better than native 1440p. That‘s why I’m asking how mac copes with that scaling.
 

Christopher Kim

macrumors 6502a
Nov 18, 2016
703
664
FWIW, I am running my 2016 13" MBP (w/ Touch Bar / 4 TB3 ports) closed clamshell into a 27" LG 4K monitor (27UD68). I also really wanted to run an effective resolution of 2560x1440, as I think for a 27" monitor, that resolution is the best size for text / icons (true 4K everything too small, and 1080p too big), and really wanted to utilize Apple's smooth HiDPI / pixel-doubling for extra smoothness (just like the 27" iMac or 27" UltraFine 5K).

In the end, cost was a bigger factor, as the LG 27UD68 is really nice bang-for-buck, so I bought it. Honestly, I couldn't notice a difference running it at "Looks like 1920 x 1080" (which would be true 4x1 pixel doubling / HiDPI) and "Looks like 2560 x 1440" (which uses Apple scaling). When I first got it, I tried both resolutions extensively and both looked just as smooth. I also had zero performance issues running it at 2560 x 1440, although granted, I don't play games nor do I do things like video editing that really push performance. As such, I've been using "Looks like 2560 x 1440" for years, and have been very happy with it.
 

schmorf

macrumors newbie
Original poster
Apr 22, 2020
9
8
FWIW, I am running my 2016 13" MBP (w/ Touch Bar / 4 TB3 ports) closed clamshell into a 27" LG 4K monitor (27UD68). I also really wanted to run an effective resolution of 2560x1440, as I think for a 27" monitor, that resolution is the best size for text / icons (true 4K everything too small, and 1080p too big), and really wanted to utilize Apple's smooth HiDPI / pixel-doubling for extra smoothness (just like the 27" iMac or 27" UltraFine 5K).

In the end, cost was a bigger factor, as the LG 27UD68 is really nice bang-for-buck, so I bought it. Honestly, I couldn't notice a difference running it at "Looks like 1920 x 1080" (which would be true 4x1 pixel doubling / HiDPI) and "Looks like 2560 x 1440" (which uses Apple scaling). When I first got it, I tried both resolutions extensively and both looked just as smooth. I also had zero performance issues running it at 2560 x 1440, although granted, I don't play games nor do I do things like video editing that really push performance. As such, I've been using "Looks like 2560 x 1440" for years, and have been very happy with it.
Thank you very much! Sharing your experience was very helpful! Very glad to hear that. My intention was the same. I think I will also go with the 27“ 4K monitor and hope I will not be disappointed.
Do you experience any hick ups when watching a 4K Video on YouTube?
 

Philipp Kyeck

macrumors newbie
Apr 23, 2020
2
0
Berlin, Germany
@schmorf Please post an update, whenever you had the time to check it out yourself. I'm also thinking about upgrading my 27" 1440p monitors to 4K ... but only if it's worth it. And the MacMini2018 can run them both without melting ;)
 

schmorf

macrumors newbie
Original poster
Apr 22, 2020
9
8
@schmorf Please post an update, whenever you had the time to check it out yourself. I'm also thinking about upgrading my 27" 1440p monitors to 4K ... but only if it's worth it. And the MacMini2018 can run them both without melting ;)
I definitely will! Not sure when I will finally place the order but probably during next week.
 

onepoint

macrumors 6502a
Aug 3, 2010
857
556
USA
These same questions are why I went with the LG 34WN80C-B. I have my MacBook Pro 13 in clamshell mode, connected over USB-C, driving the monitor at native 3440x1440 resolution - sitting at my normal viewing distance I don't notice any pixelation or fuzziness and I'm beyond happy with the choice.
 
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bill-p

macrumors 68030
Jul 23, 2011
2,886
1,548
This will only affect performance when you have large desktop animations like, say... Launchpad or something like that. It'll be perfectly okay if you don't ever use Launchpad. Ever.

It'll also be perfectly okay if you don't visit websites that have whole full screen animations.

It'll also be okay if the apps you use don't do full screen animations.

It'll also be okay if you don't play games.

It'll also be okay if you don't try to watch 1440p or 4K videos in Youtube in Chrome.

So it highly depends on how you're going to use the computer.

Also, I had a 2020 MacBook Air and it's far less smooth than my 2018 MBP 13" at running my 34" WK95U (5K2K resolution) for what that's worth. I had to disable transparency even at the default "looks like 2560 x 1080" resolution just to get "on-par" performance, but that's probably just me. Your mileage may vary.

In comparison, my 16" MacBook Pro is perfectly fine at all scaled resolutions. Far more than my 13" MBP. If you need a comparison.
 
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schmorf

macrumors newbie
Original poster
Apr 22, 2020
9
8
This will only affect performance when you have large desktop animations like, say... Launchpad or something like that. It'll be perfectly okay if you don't ever use Launchpad. Ever.

It'll also be perfectly okay if you don't visit websites that have whole full screen animations.

It'll also be okay if the apps you use don't do full screen animations.

It'll also be okay if you don't play games.

It'll also be okay if you don't try to watch 1440p or 4K videos in Youtube in Chrome.

So it highly depends on how you're going to use the computer.

Also, I had a 2020 MacBook Air and it's far less smooth than my 2018 MBP 13" at running my 34" WK95U (5K2K resolution) for what that's worth. I had to disable transparency even at the default "looks like 2560 x 1080" resolution just to get "on-par" performance, but that's probably just me. Your mileage may vary.

In comparison, my 16" MacBook Pro is perfectly fine at all scaled resolutions. Far more than my 13" MBP. If you need a comparison.
Thank you very much for clarification and the comparisons between your devices!

I never thought it would be this complicated when I decided to get a new external monitor. My current monitor is a 22 inch 1680x1050 from 2008 and when I spend around 400 - 600 dollars for a new monitor I want it to be future proof for at least 5 years - and I'm not sure if 1440p is. I went with the Air because I mostly read/write text. That's why I wanted the text to look as sharp as possible on my external monitor. But surfing the web and watching videos on YouTube is also a big part of my usage, and thinking about watching a video with constant hick ups with devices from 2020 makes me nervous.

@onepoint This is very understandable, I might save some money and go with a 1440p screen as well.

I will think about it and keep you guys updated.

Edit: I knew that the Air wouldn't be a power house. But I don't think watching 4K videos on a 4K screen is a "pro" task, especially when the Air supports up to 6K displays.
 
Last edited:

xraydoc

Contributor
Oct 9, 2005
10,771
5,227
192.168.1.1
Edit: I knew that the Air wouldn't be a power house. But I don't think watching 4K videos on a 4K screen is a "pro" task, especially when the Air supports up to 6K displays.
It’s a side effect of how the Mac does retina screen resolution scaling. To do 1440p “retina” on a 4K monitor, the Mac will actually in memory render a 5120x2880 screen image, then shrink it down to fit on the 4K monitor. It’s this supersized rendering that causes the performance hit if it requires math other than an exact 2x multiple of the display’s native resolution.

Macs with dedicated GPUs can do this way faster, so much less performance hit, but at expense of much higher power/battery usage.

Windows takes a very different approach. Much lower performance hit but causes some other issues not found in Apple’s method.
 

schmorf

macrumors newbie
Original poster
Apr 22, 2020
9
8
It’s a side effect of how the Mac does retina screen resolution scaling. To do 1440p “retina” on a 4K monitor, the Mac will actually in memory render a 5120x2880 screen image, then shrink it down to fit on the 4K monitor. It’s this supersized rendering that causes the performance hit if it requires math other than an exact 2x multiple of the display’s native resolution.

Macs with dedicated GPUs can do this way faster, so much less performance hit, but at expense of much higher power/battery usage.

Windows takes a very different approach. Much lower performance hit but causes some other issues not found in Apple’s method.
Yeah I know, it's extremely unfortunate.

But even with a dedicated GPU I feel it's kinda stupid that a good portion of it is busy with just the scaling...
 

Christopher Kim

macrumors 6502a
Nov 18, 2016
703
664
It’s a side effect of how the Mac does retina screen resolution scaling. To do 1440p “retina” on a 4K monitor, the Mac will actually in memory render a 5120x2880 screen image, then shrink it down to fit on the 4K monitor. It’s this supersized rendering that causes the performance hit if it requires math other than an exact 2x multiple of the display’s native resolution.

That makes sense. When I'm running "looks like 2560x1440" into my 27" 4K monitor, when I pull up System Report > Graphics/Displays, it shows as Resolution: 5120 x 2880 (5K / UHD+), and then UI Looks Like: 2560 x 1440 @ 60Hz, so can confirm the Mac is doing the HiDPI pixel-doubling to 5K, and then scaling the 5K image down to fit on the 4K monitor. I guess that process is why it looks better than if it just showed a native 2560 x 1440 image (which is then scaled up to fit on the 4k monitor).

So. makes sense that it follows that performance for this will depend a lot on the hardware you have. My 2016 13" MBP has a decent processor (2.9ghz quad-core I5, this is 6th gen Intel Skylake) and integrated graphics. I'm sure the 15" MBP with dedicated GPU does even better. Someone smarter than me who understands how OP's 2020 MacBook Air would compare.
 
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Fishrrman

macrumors Penryn
Feb 20, 2009
28,327
12,451
OP wrote:
"This is very understandable, I might save some money and go with a 1440p screen as well."

Running a "native" 1440p display at 1440p is going to "put the least amount of load" on the MacBook, particularly the MacBook Air. Sumthin' tells me it will just run much better (and cooler) that way.

I haven't really investigated the 27" 1440p displays "out there", because (at least to me), 32" @ 1440p would look to be better. But my eyes are getting older and the pixel size of .277mm isn't objectionable.
Pixel size on a 27" 1440p display will be .234mm. Perhaps better on younger eyes.

For 32" displays, the HP "Omen" looks to be the nicest, but it's a little pricey. It seems to get the best reviews ...
 

schmorf

macrumors newbie
Original poster
Apr 22, 2020
9
8
Running a "native" 1440p display at 1440p is going to "put the least amount of load" on the MacBook, particularly the MacBook Air. Sumthin' tells me it will just run much better (and cooler) that way.
It will definitely run better! I’m just not sure if 1440p is future proof when every smartphone can take videos at 4K since 2016.
I haven't really investigated the 27" 1440p displays "out there", because (at least to me), 32" @ 1440p would look to be better. But my eyes are getting older and the pixel size of .277mm isn't objectionable.
Pixel size on a 27" 1440p display will be .234mm. Perhaps better on younger eyes.
Well, I have also never owned a 27 inch 1440p monitor but 1440p seems to be the „sweet spot“ for most people.
 
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3lmanana

macrumors newbie
Jun 5, 2020
2
0
I had the same problem and desire to purchase the future-proof monitor before doing any investigation.

I bought LG 27UK670, basically a 27” 4K display with USB-C.

At home I have both PC and MacBook Pro 15 2018 (6 core i7, RX560) and it doesn’t run smooth on any device.

It works better on Macbook Pro, but you can feel UI lagginess. I have also read that even iMac Pro doesn’t run super smooth (5K display with 2x scaling factor).
 

aednichols

macrumors 6502
Jun 9, 2010
381
311
At home I have both PC and MacBook Pro 15 2018 (6 core i7, RX560) and it doesn’t run smooth on any device.
This may seem ridiculous, but have you tried plugging your display into the other side of your MBP? Ever since the 2016 generation there have been undocumented differences between the left- and right-hand USB C ports.

For reference, I have a 2016 15" unit with a Radeon Pro 455 connected to a Dell P2715Q @ 2560x1440 and performance is flawless (and I am one to notice these things).
 

macuserNL86

macrumors newbie
Nov 11, 2020
1
0
I was just facing the same issue. After having set up my screen and it offered scaling I had to reset my monitor and all I could do was change the resolution. Result: Fuzzy screen.
I went into my monitor settings and change from DisplayPort 1.1 to DisplayPort 1.2.
When I went back into System Preferences > Display I could scale my external monitor again, instead of just change the resolution.

Hope this helps others too.
 

mfram

Contributor
Jan 23, 2010
1,307
343
San Diego, CA USA
I have a 2020 13" MBP. I run my 27" 4K displays at "looks like 1440p" and I think they look great. I don't really notice any graphics glitches. But then again, I'm not terribly sensitive to them anyway. I previous had a 27" monitor at 1440p native and I can definitely say that the 4K monitors feature text that is much sharper than the old monitor. I have an LG monitor and a Dell. My Dell has much better color reproduction (it's a higher quality monitor) but the text looks great on both monitors.
 

iordash

macrumors newbie
Mar 2, 2020
8
1
I have a 2020 13" MBP. I run my 27" 4K displays at "looks like 1440p" and I think they look great. I don't really notice any graphics glitches. But then again, I'm not terribly sensitive to them anyway. I previous had a 27" monitor at 1440p native and I can definitely say that the 4K monitors feature text that is much sharper than the old monitor. I have an LG monitor and a Dell. My Dell has much better color reproduction (it's a higher quality monitor) but the text looks great on both monitors.
I wanna buy a 27 inch monitor, and like you said i want to use in 1440p, so it's better to buy 4k monitor ?not an 1440p?

My macbook pro 13 inch display is set to looks like 1440x900. Thanks
 

deeddawg

macrumors G5
Jun 14, 2010
12,245
6,393
US
I wanna buy a 27 inch monitor, and like you said i want to use in 1440p, so it's better to buy 4k monitor ?not an 1440p?
Kinda depends on the person. Some folks think 4K scaled to 1440p looks better than straight up 1440p. Other folks think straight up 1440p is just fine. Do note that scaling does use more computer resources than just driving the display with no scaling. I also believe fractional scaling such as 1440p on 4K (1:1.5) uses more resources than integer scaling like 1080p on 4K (1:2).

Personally I like direct QHD (1440p) on 27" - and am considering an upgrade to UW-QHD which adds greater width while retaining the 1440p vertical resolution.


My macbook pro 13 inch display is set to looks like 1440x900. Thanks
Not entirely relevant since external monitor resolution sweet spot also depends on your viewing distance from the monitor. That said, I find with a typical workdesk setup / monitor distance, QHD on 27" gives a familiar feel to 1440x900 on a 13" laptop display.
 
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