Very confused about my iMacs 5k Resolution

moosed

macrumors newbie
Original poster
Mar 10, 2017
21
0
So my 5k iMac screen got cracked, I ordered a new one to fit myself as the computer is out of warranty.

I've attached it and its working but 5k resolution isn't available and when i click on the Displays setting in 'About this mac' it says that its 3840x2160.



However when i go to resolution settings the max available one is 3360x1890 and that my default resolution looks like 1080p.



However when i go to the system information screen it says its a 5k display...



Anyone idea what could be going on ? Im bemused

If anyone else here had a 5k iMac could you do me a favour and look at your display settings and see what your maximum scaled resolution is ?
 

NT1440

macrumors G5
May 18, 2008
12,325
15,413
If you choose the "More space" option you'll get closer to the full 5K resolution.

5K on Macs isn't to get 5K native resolution displayed (everything would be TINY). It's to mimic the standard resolutions available on that size screen but with a much sharper image.
 

moosed

macrumors newbie
Original poster
Mar 10, 2017
21
0
Hi

yes i realise 5k on a 27" would be ridiculously tiny but what I'm confused about is that when i select 'default for my display' it uses a resolution which 'looks like 1080p'... however i swear on my previous screen it used a higher looking resolution and i swear the max scaled resolution was 5120x2880.

Or is my memory failing me ?
 

NT1440

macrumors G5
May 18, 2008
12,325
15,413
Hi

yes i realise 5k on a 27" would be ridiculously tiny but what I'm confused about is that when i select 'default for my display' it uses a resolution which 'looks like 1080p'... however i swear on my previous screen it used a higher looking resolution and i swear the max scaled resolution was 5120x2880.

Or is my memory failing me ?
I've never owned a 27" so I can't comment on the max scaled resolutions, what happens when you select the option all the way to the right under "more space"? I imagine that's going to get you closer to what you're looking for.
 

moosed

macrumors newbie
Original poster
Mar 10, 2017
21
0
Yes that obviously gives me a crazy small resolution which it says 'looks like 3360x1890'... its not so much that i want to run these crazy resolutions... i just want to make sure i've purchased the correct replacement screen !

It would be great if someone else with a 5k iMac could confirm that this is the correct resolution for the maximum scaled value
 

sartrekid

macrumors 6502a
Oct 30, 2014
533
511
Germany
Hi

yes i realise 5k on a 27" would be ridiculously tiny but what I'm confused about is that when i select 'default for my display' it uses a resolution which 'looks like 1080p'... however i swear on my previous screen it used a higher looking resolution and i swear the max scaled resolution was 5120x2880.

Or is my memory failing me ?
The max scaled resolution on the 5k iMac "looks like" 3200 x 1800.
 

moosed

macrumors newbie
Original poster
Mar 10, 2017
21
0
The max scaled resolution on the 5k iMac "looks like" 3200 x 1800.
See this is what is so confusing to me, mine is 3360x1890.

Also when i click the 'default for display' button it switches to a res which 'looks like 1920x1080' but when i click the default button in the scaling it uses a resolution which 'looks like 3080x1692'

utterly confusing, something is clearly muddled up.

Does anyone know of any kind of process/driver reset i need to do when replacing a screen ? or should it just be plug and play ?
 

theluggage

macrumors 601
Jul 29, 2011
4,673
3,511
yes i realise 5k on a 27" would be ridiculously tiny but what I'm confused about is that when i select 'default for my display' it uses a resolution which 'looks like 1080p'...
I'd have thought "Default for display" on a 5k iMac should be "Looks like 2560x1440" (the old pre-5k resolution).

3840x2160 is standard UHD as per so-called "4k" displays (which would default to "looks like 1080p").

Sounds odd - you still need a 5k owner to confirm what a working 5k displays...
 

sartrekid

macrumors 6502a
Oct 30, 2014
533
511
Germany
I'd have thought "Default for display" on a 5k iMac should be "Looks like 2560x1440" (the old pre-5k resolution).

3840x2160 is standard UHD as per so-called "4k" displays (which would default to "looks like 1080p").

Sounds odd - you still need a 5k owner to confirm what a working 5k displays...
I am a 5k owner and gave the data...
 

moosed

macrumors newbie
Original poster
Mar 10, 2017
21
0
I'd have thought "Default for display" on a 5k iMac should be "Looks like 2560x1440" (the old pre-5k resolution).

3840x2160 is standard UHD as per so-called "4k" displays (which would default to "looks like 1080p").
Yes, my previous screen defaulted to 2560x1440 when i clicked 'default for this display' but now when i do that it selects a resolution that 'looks like 1080p'

The weirdest thing is that if i click the 'default' scaling tile in that screen it shows a resolution that 'looks like 3008x1692'

I have the option to use 2560x1440 though... but its the middle scaling option and not listed as default. It looks correct though.

So friggin confused. I don't understand how swapping out a screen could cause this ?

It clearly says in the system information screen that the display is 5120x2880... so it must be the correct screen ?
 

moosed

macrumors newbie
Original poster
Mar 10, 2017
21
0
Thank you.

I take it the default middle one is 2560x1440 ?

This is the same as what my previous screen was like. With this other one my resolution options are different.

Im so confused. Thinking about reinstalling OSX and seeing if they go back to normal scaling options.
 

NT1440

macrumors G5
May 18, 2008
12,325
15,413
Thank you.

I take it the default middle one is 2560x1440 ?

This is the same as what my previous screen was like. With this other one my resolution options are different.

Im so confused. Thinking about reinstalling OSX and seeing if they go back to normal scaling options.
Before doing so, it wouldn't hurt to do an NVRAM reset, it's quicker than a re-image. Probably won't solve it, but it's quick and worth the shot.
 

Dustman

macrumors 65816
Apr 17, 2007
1,299
101
Thank you.

I take it the default middle one is 2560x1440 ?

This is the same as what my previous screen was like. With this other one my resolution options are different.

Im so confused. Thinking about reinstalling OSX and seeing if they go back to normal scaling options.
Try resetting your PRAM and SMC.

PRAM:

Reboot whilst holding CMD+OPTN+R+P until you hear a chime a second time.

SMC:

Turn off Mac
Unplug power cable
Hold power button for 5+ seconds
Plug in, and turn on
 

moosed

macrumors newbie
Original poster
Mar 10, 2017
21
0
Thanks for the suggestions. I've tried both of those but no joy.
[doublepost=1489177182][/doublepost]
Here are the screenshots
Hi. I have one more request if thats ok ? could you go to 'about this mac', click on 'displays' and post a screenshot of that... or tell me what it says the resolution is.

Cheers
 

moosed

macrumors newbie
Original poster
Mar 10, 2017
21
0
Here's what my 5K states:

About This Mac > Displays > Built-in Retina Display 27-inch ( 5120 x 2880 )
Thanks. Hmm... I'm so confused right now.

Why would mine show 3840x2160 but 5120x2880 in the system information screen.
 

jerwin

macrumors 68030
Jun 13, 2015
2,840
4,634
Screen Shot 46.png


Hold down the option key while clicking on the "Scaled" radio button.

I usually leave it at 2560x1440 but the native resolution is occasionally very useful for browsing digital archives*-- as well as certain older games.


*for instance, the new yorker archives are legible as two page spreads-- if you boost the resolution, and have sufficient bandwidth.
 

moosed

macrumors newbie
Original poster
Mar 10, 2017
21
0
View attachment 691794

Hold down the option key while clicking on the "Scaled" radio button.

I usually leave it at 2560x1440 but the native resolution is occasionally very useful for browsing digital archives*-- as well as certain older games.


*for instance, the new yorker archives are legible as two page spreads-- if you boost the resolution, and have sufficient bandwidth.
Hi. Thank you for taking the time to repond.

I am aware of this shortcut however the issue is that my native resolution should be 2560x1440 but it is instead listed as 1920x1080. 2560x1440 is now a scaled resolution whereas on the previous screen it was the native resolution.

Looking at your screenshot you do not even have 1920x1080 as a selectable resolution.

It is as if the iMac thinks its a 3840x2160 monitor for some reason, but still lists it as 5120x2880 in the system information screen.

It makes no sense whatsoever. I cannot find a single thing about this anywhere on the internet :(
[doublepost=1489186416][/doublepost]I think i've just sussed it out

I found this in a listing for my display

if your model is 5K Late 2015, it is 100% compatible with LM270QQ1 SDA2.
if your model is 5K Mid 2015 or Late 2014, The maximum resolution is 4K.

Doh ! and yet its listed as 5k in the system information. I guess for some bizarre reason it's not supported to display at that resolution
 

jerwin

macrumors 68030
Jun 13, 2015
2,840
4,634
if your model is 5K Late 2015, it is 100% compatible with LM270QQ1 SDA2.
if your model is 5K Mid 2015 or Late 2014, The maximum resolution is 4K.
Ouch! Apple did have to design some custom circuitry (the "TCON") to get a 5K display before Display Port et al were ready. Perhaps the 2015 models have more of an industry standard design.
 
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