External monitor for 27 inch iMac

[Dr. McKay]

I have a 27 inch iMac, 2017 model with 5K Retina display and I'd like to buy an external 27 inch display as an extension.

iMac "Core i5" 3.5 27" (5K, Mid-2017) Specs (Retina 5K, Mid-2017, MNEA2LL/A, iMac18,3, A1419, 3070): EveryMac.com

Technical specifications for the iMac "Core i5" 3.5 27" (5K, Mid-2017). Dates sold, processor type, memory info, hard drive details, price and more.

everymac.com

Apparently, it's not as straightforward as it seems because it seems that a 4K display can cause problems with resolution scaling, performance and image sharpness.
I was looking at 4K monitors but 1440p is said to be much better.

Any suggestions ?

 

[Hat Tric]

Short answer: If you can afford it, why not get the Mac Studio Display. It will be just as gorgeous and fully retina like your current iMac screen and it's compatible with your 2017 model.

Long answer: read these links as they are the most comprehensive on the topic of "retina" displays

Mac external displays for designers and developers, part 2

Since writing about Mac external displays in 2016, not much has changed. LG, Dell, Samsung, and other display makers have either never catered for the specs many Mac designers and developers want, or they’ve reluctantly produced products that have been short-lived or compromised.

bjango.com

https://bjango.com/articles/macexternaldisplays/ (some more details, written before Mac Studio)
https://www.caseyliss.com/2021/12/7/monitor-liss (this was written before Mac Studio display)

 

[Dr. McKay]

Short answer: If you can afford it, why not get the Mac Studio Display.

No way...
I don't need a high-end colour accurate display, it's for working in a DAW for music production.
Just looking for a decent 27" monitor, nothing more, $400 - $500 tops.

I came across this video, wonder if there is any truth to it...

 

[Nguyen Duc Hieu]

I have a 27 inch iMac, 2017 model with 5K Retina display and I'd like to buy an external 27 inch display as an extension.

iMac "Core i5" 3.5 27" (5K, Mid-2017) Specs (Retina 5K, Mid-2017, MNEA2LL/A, iMac18,3, A1419, 3070): EveryMac.com

Technical specifications for the iMac "Core i5" 3.5 27" (5K, Mid-2017). Dates sold, processor type, memory info, hard drive details, price and more.

everymac.com

Apparently, it's not as straightforward as it seems because it seems that a 4K display can cause problems with resolution scaling, performance and image sharpness.
I was looking at 4K monitors but 1440p is said to be much better.

Any suggestions ?

I would just buy a 1440p monitor, just to be sure.

 

[theluggage]

No way...
I don't need a high-end colour accurate display, it's for working in a DAW for music production.
Just looking for a decent 27" monitor, nothing more, $400 - $500 tops.

Problem with the 4k vs 1440p issue is: complicated issue is complicated. It's also somewhat subjective & dependent on what you are mostly using your computer for.

I wrote a long screed about it here: https://forums.macrumors.com/threads/psa-4k-display-resolutions.2345906/?post=31127104#post-31127104

TLNR is that: many people want to run their 4k display in "looks like 2560x1440" scaled mode to get the same sized system fonts, icons, menus etc. as the default setting on a 5k iMac. That is very effective in general use and gives a far sharper image than you'd get from an actual 1440p display. However, this places extra load on the GPU/VRAM (which may be a problem if you're doing 3D or other work which already stresses the GPU) and stops you displaying photos etc. so that 1 pixel in the original corresponds exactly to 1 pixel on the display (which may be an issue if you're doing a lot of photo editing). Both of these can be avoided by using the (usually default) "looks like 1920x1080" mode - at the expense of making system fonts, icons, menus etc.rather large (whether that means "too large" is one of those subjective, "your mileage may vary" things).

Since you're not earning your crusts from photo editing or 3D work I'd recommend a 4k display if you find one in your price range. It's far more versatile. 1440p would get the job done, and maybe save you some money, but it's going to look really fuzzy alongside a 5k iMac. I don't think the GPU load would be a problem unless, maybe, you got the cheapest 5k iMac - and you still don't have to run it in scaled mode.

(Note: the video you linked was someone using demanding 3D software on a Mini which was struggling anyway. They had a good reason for sticking to 1440p).

You might also want to consider what your display needs will be if you come to buy a new Mac, since the 27" iMac option is now off the table & you'll be looking at a Mini, Studio or MacBook + external display.

I personally like the Huawei Mateview 28.2" - which is the same width & pixel density as a 27" 4k but with an extra 2.5" high strip added on the bottom. Unfortunately, I don't think it's widely available in the US.

 

[gilby101]

I was looking at 4K monitors but 1440p is said to be much better.

As has been said:

many people want to run their 4k display in "looks like 2560x1440" scaled mode to get the same sized system fonts, icons, menus etc. as the default setting on a 5k iMac. That is very effective in general use and gives a far sharper image than you'd get from an actual 1440p display.

4K 27" is the way to go. Yes, there is some compromise in terms for clarity/sharpness, but it is either that or a 5K display (beyond your budget).

 

[kaintxu]

As has been said:

4K 27" is the way to go. Yes, there is some compromise in terms for clarity/sharpness, but it is either that or a 5K display (beyond your budget).

The thing is, the scaling it does when you run it as 1440p how does it affect the gpu? What is the compromise?

 

[gilby101]

The thing is, the scaling it does when you run it as 1440p how does it affect the gpu? What is the compromise?

With a 4K screen running as look like 1440p, the virtual display on which applications draw/write is 5120x2880 pixels which is then scaled down to 4K send to the screen. So compared with a 5K screen (which also draws as 5120x2880), there is extra memory and CPU/GPU when you use 4K screen. But, unless the Mac is under memory pressure, you probably wouldn't notice the difference. In addition, I would be wary adding any second screen on a Mac with 8 GB RAM - neither you nor the OP mention your RAM or GPU spec.

 

[kaintxu]

With a 4K screen running as look like 1440p, the virtual display on which applications draw/write is 5120x2880 pixels which is then scaled down to 4K send to the screen. So compared with a 5K screen (which also draws as 5120x2880), there is extra memory and CPU/GPU when you use 4K screen. But, unless the Mac is under memory pressure, you probably wouldn't notice the difference. In addition, I would be wary adding any second screen on a Mac with 8 GB RAM - neither you nor the OP mention your RAM or GPU spec.

I am on a 2019 i5 9600k with vega 48 and 24 GB RAM.

im trying to decide between 4k 60hz or 1440p and 180hz. It’s a hard choice and not sure which way to go. The screen is as a second monitor for my Mac, but when I work from home it will be the main monitir for windows work laptop.

bigges use is work laptop, then second monitor to play TTS and some virtual tablets for rpg such as foundry or roll20 and there will be some gaming, but I think most of the gaming will happen on the 5k display anyway, so that’s my doubt. To go with my iMac maybe 1440p was enough as secondary, but for work 4K is clearly better.

and there comes my issue of the performance but wi5 my specs using 4K as 1440p on iMac vs the refresh rate of a 1440p at 180hz

 

[gilby101]

I am on a 2019 i5 9600k with vega 48 and 24 GB RAM....and there comes my issue of the performance but wi5 my specs using 4K as 1440p on iMac vs the refresh rate of a 1440p at 180hz

With that spec, you should have no performance issues with a 4K as 1440p. Only you can decide which is better for your use case - seems like work vs games.

 

[kaintxu]

With that spec, you should have no performance issues with a 4K as 1440p. Only you can decide which is better for your use case - seems like work vs games.

Hi,

I finally went for a 27” 4K display with up to 160hz. The LG 27GP950b as there was a great offer for 550€

right now I have both the 27gp850b 1440p and the 27gp950 4K in front of me hooked to my iMac and for some reason I can’t get over 95hz on the 4K while the 1440p can do 164hz. Any idea why I lose the option when the monitor is supposed to be able to drive those hz?