New 4K monitor. UI size is fine, but images are screwed up!

[johntheeditor]

Running Mac OS 10.14.6 and Photoshop 21.2.3. I just switched from a 1920 x 1200 monitor to a 4K (16:9) monitor whose native resolution is 3840 x 2160. I have the Mac's display preferences set to simulate 2560 x 1440 — this makes the user interface the right size across programs.

The problem is that if I make a new document of 3840 x 2160, it appears significantly smaller than the screen - about 75% of the screen size when Photoshop is set to display at 100%. I work a lot with screen-only images, and I want Photoshop to display actual 100% when set to display at 100%.

When the new document is set to the scaled size of 2560 x 1440, it appears MUCH smaller than the screen.

How can I make Photoshop display 100% at 100%? I don't remember having to do anything special before I switched monitors. 

TIA.

[NB, colourmanagement net]

Hi

I hope I understood your explanation - The difference between your previous setup and now seems to be that you have the Mac's display preferences set to simulate 2560 x 1440. I expect that if you use the full screen resolution in your Mac's system preferences/ displays control panel then you'll see Photoshop behave normally at 100%. 

It seems perverse to buy a 4K screen and not allow it to run at full resolution. Of course, if text in dialog boxes and icons etc are too small to read then that's another issue. 

I am not lucky enough to have a 4K display to test but I wonder if this info helps: https://www.macobserver.com/tips/how-to/4k-monitor-retina-mode/

I hope this helps

thanks
neil barstow, colourmanagement.net :: adobe forum volunteer
[please do not use the reply button on a message within the thread, only use the blue reply button at the top of the page, this maintains the original thread title and chronological order of posts]

[johntheeditor]

Hi, Neil—thanks for the reply! The article you linked to explains: "regardless of which option you choose here your Mac will still be sending information to your screen at full resolution, it will just be using those extra pixels to smooth out the elements it is displaying." The settings affect UI scaling, not actual pixel resolution. (My Mac's settings match the screenshots in the article.)

On further investigation, my problem seems to be that my Mac detects the monitor as having pixel dimensions of 5120 x 2880, when in fact its dimensions are 3840 x 2160. In fairness, this doesn't seem to be an Adobe problem, and I should investigate with Lenovo and with Apple. Although if anyone else reading this can shed light on the problem, I'd love to hear it!

Thanks,
John 

[D Fosse]

It seems to me this should resolve itself if you allow the monitor to run at native resolution (which also gives you what you have paid for).

AFAIK no Macs have a native resolution of 3840 x 2160, and the forced screen scaling is probably set up to mimic only native screen dimensions. So 5K is the closest it can find.

[johntheeditor]

I think you've misunderstood the nature of the scaling provided by the Displays panel. In general, it affects only the size of the UI, not the actual resolution of the display. There is a "2560 x 1440 (low resolution)" setting available as a hidden option which would actually changhe the resolution, but that's not what I have selected.

The problem is that the Mac is somehow detecting this 4K monitor as being a 5K monitor. I need it to correctly detect the native resolution of the display so that Photoshop works correctly.

[NB, colourmanagement net]

Hi John

thanks for your thanks

if your mac neither detects the display correctly nor offers the correct resolution as an option then this surely is a question for Apple and Lenevo, I agree. 

Perhaps the display's native resolution is not supported by the video card in your Mac?  That should be relatively easy to find out.

This article I found from Dell may help: 4K & 5K High Resolution Display support by Mac systems - Dellwww.dell.com › Supporto › Knowledge Bas...

It's also likely somewhat dependent on how its connected, cable types and even with the right type the way they are made can cause display screen issues. I am an Eizo reseller and they seem to generally recommend Startech:
I asked about USB-C connection - Eizo replied "this is not so simple as you need to buy appropriate cables and the folk at EIZO have tested and now recommend the following cable:

• USB-C to DisplayPort Adapter Cable – 6 ft (1.8m) – 4K at 60 Hz (product ID: CDP2DPMM6B)"

In the UK we have a very efficient free 'call back' support service from Apple - I hope it’s the same for you, that option should be obvious if you go through the support interface at Apple's website. 

Please report back here with the solution as it will, no doubt, be of help to others

I hope this helps

thanks
neil barstow, colourmanagement.net :: adobe forum volunteer
[please do not use the reply button on a message within the thread, only use the blue reply button at the top of the page, this maintains the original thread title and chronological order of posts]

[johntheeditor · Accepted solution]

Neil: I got the answer from Stephane Madrau, the developer of SwitchResX, a display resolution utility for the Mac. (I've bought it and recommend it.) Stephane says:

"All is normal.

You have a 4K monitor, all your resolutions are using a 4K signal that is sent to the monitor.

Long answer:

The EDID mentions this as its preferred (native) resolution :

Descriptor #0 - Timing definition:
Mode = 3840 × 2160 @ 59.997Hz

Then, when you use System Preferences to set up 2560x1440 (HiDPI), macOS will generate a 5120x2880 internal image. That's the definition of the hiDPI: it scales the whole UI to 200%, so each pixel that you see will use 4 sub-pixels. So a 2560x1440 HiDPI is internally a 5120x2880 picture (and a 1280x800 HidPI would be 2560x1600, etc).

That's what System Information reports: your UI is 2560x1440, but the internal framebuffer (the memory keeping the picture before being sent to the monitor) is 5120x2880. That's why other tools will report 5120x2880, and also why a screenshot of the whole screen will produce a 5120x2880 picture.

At the end, this 5120x2880 picture will be sent to the monitor on a video signal. The video signal being 4K, the Mac will scale the 5120x2880 to 3840x2160. This effectively removes 44% of the pixels, and this is done by dithering the picture in memory. At the end it's invisible because your 2560x1440 resolution is not using 4 sub-pixels for each pixel, but 56% of these 4 pixels, with picture scaling in real time.

Photoshop on its side will think the picture is a 5K picture and will bypass this picture scaling, showing everything like it would be 5K. It *is* effectively 5K, but only in memory. The monitor on its side is showing a scaled down picture."

(Me again) To resolve my problem in Photoshop, I can switch to a simulated 1920 x 1024 resolution—or to the native 3840 x 2160 resolution, if I'm willing to work with tiny interface items. A 1920 x 1024 resolution is internally scaled to 3840 x 2160, the native resolution of the monitor, and images that I create in Photoshop are proportioned correctly.

Thanks for your help!

[davescm]

Hi

The key to understand this, is what is meant by 100% in Photoshop. It is not a phsyical size. It simply means 1 image pixel mapped onto 1 screen pixel. It does that to avoid any scaling on screen. Any scaling in the display chain introduces artifacts and blurring, and especially any that does not have a direct 1:1  or 4:1  or 9:1 or 16:1 etc ratio. 

Photoshop, as a professional image application, must provide a non scaled , zero artifact view. Without that then we do not know whether our image is accurate or not.

If you want a larger on screen image , then Photoshop gives you the option of 200% zoom which will use 4 screen pixels for 1 image pixel.