Color Depth Incorrect on External Monitor (LG 27UP600)

[rm5]

Hey, y'all, I am having a VERY strange issue with my external monitor, which is most noticeable in dark mode, and it is really getting on my nerves. Basically, I see this pattern all over the place, and I am told that this is because macOS is setting the color depth incorrectly. You can see what I'm talking about in the attached images. I am using an LG 27UP600 monitor, and have tried changing EVERY setting on the OSD, including factory-resetting the display, all of which don't fix the issue. I have also not found a way to fix this issue in macOS, either. Google and YouTube have been of no help.

Does anyone know if this is indeed the problem, and how to fix it? Any help appreciated as always!

EDIT: I should clarify that both these images are of the external monitor, NOT the built-in iMac display.

 

[Bigwaff]

Your screenshot indicates you are using the built-in display but you state you are using an external monitor.

 

[rm5]

Your screenshot indicates you are using the built-in display but you state you are using an external monitor.

Everything in these pictures is on the external monitor, not the built-in display. I apologize if there was confusion there. The purpose of that photo was to demonstrate the "streaks" (idk what else to call them). The fact that "built-in display" is in the photo is irrelevant and should be disregarded, as any and all content photographed was on the external display.

 

[Bigwaff]

Please post a picture with the external monitor selected so we can see the settings for the external monitor.

 

[rm5]

Of course!

 

[joevt]

Which Macs have you tried this on?
If you have an Intel Mac with the problem, then post the output of AllRez. Run this command:

./allrez > lgmonitor_allrez.txt

Zip the result and post as an attachment.

 

[rm5]

Here you go!

 

[rm5]

I should note that this problem is on my 2019 21.5" iMac, it does not happen on my M1 MacBook Air when connected to the same monitor.

 

[joevt]

Here you go!

It says you are using an HDMI 2.0 timing mode, 5K framebuffer (2560x1440 HiDPI mode) scaled down to 4K (because the LG is a 4K display), using 4:2:0 chroma sub-sampling, 10bpc.

But I don't think that should cause the strange gradient. 4:2:0 reduces color resolution, not color depth.

How is the display connected? Have you tried connecting it using DisplayPort instead of HDMI?

 

[rm5]

How is the display connected? Have you tried connecting it using DisplayPort instead of HDMI?

It is connected via HDMI through an Apple Multiport Adapter. While the monitor has DisplayPort, I do not have a DisplayPort cable or adapter accessible at the moment.

I still find it extremely weird how the issue happens on this 2019 iMac, but NOT my M1 MacBook Air using the same display, cable, and adapter.

 

[joevt]

It is connected via HDMI through an Apple Multiport Adapter. While the monitor has DisplayPort, I do not have a DisplayPort cable or adapter accessible at the moment.

I still find it extremely weird how the issue happens on this 2019 iMac, but NOT my M1 MacBook Air using the same display, cable, and adapter.

Get a DisplayPort cable.

 

[Alameda]

Hey, y'all, I am having a VERY strange issue with my external monitor, which is most noticeable in dark mode, and it is really getting on my nerves. Basically, I see this pattern all over the place, and I am told that this is because macOS is setting the color depth incorrectly. You can see what I'm talking about in the attached images. I am using an LG 27UP600 monitor, and have tried changing EVERY setting on the OSD, including factory-resetting the display, all of which don't fix the issue. I have also not found a way to fix this issue in macOS, either. Google and YouTube have been of no help.

Does anyone know if this is indeed the problem, and how to fix it? Any help appreciated as always!

EDIT: I should clarify that both these images are of the external monitor, NOT the built-in iMac display.

Are you using DisplayPort or HDMI?
You should use DisplayPort if you want 10-bit color on a 4K display, because the adapter you’re using supports a maximum of 4K60 8-bit color.

It may be that on your other Mac, it runs in 4K30 mode, which can deliver 10-bit video… but scrolling is very slow.