Artifacts on Screen Using an External Monitor-Any ideas what the problem is?

[sclough]

I connected my 16 MBP to a 22" LG Ultrafine monitor. I was using it a bit this morning and then I noticed something. I typically run all my apps in full screen, but when I switched to a space that is not full screen in the top left of the screen I can see artifacts of the apps I have used previously. I've attached a screenshot and in the top left you can see faint images of the apps I had used previously. I've never seen this before--is this an issue with the display or the MBP? I had the MBP connected to a 24" 4K monitor for a day one time and never noticed this. However, I noticed it here immediately.

 

[mcnuggetswithcheese]

You are probably experiencing image persistence, and I've seen it happen in multiple displays (even on a 5K iMac). I wouldn't be too worried about it, since it usually disappears after a while.

 

[sclough]

What's also strange is that the artifacts don't appear if I do a screen shot on the Mac (shift cmd 4) but it does if I take a photo.

 

[mcnuggetswithcheese]

That is because this is a physical phenomenon of LCD displays, not a bug within macOS. Your mac is doing everything fine but I believe that your monitor needs some time to "refresh" its pixels. So if you had another external monitor and swap it with the current one when you are experiencing this issue, it shouldn't happen in the other monitor

 

[sclough]

You are probably experiencing image persistence, and I've seen it happen in multiple displays (even on a 5K iMac). I wouldn't be too worried about it, since it usually disappears after a while.

Interesting. What's strange in this case is the display had only been used about 10 minutes before today in the last week. And I only used it about 20 minutes or so and the app I first saw show up like this on the screen was only used for about 5 minutes. Seems like it should take much longer for this to happen. It's a used display so perhaps it has been heavily used in the past.
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That is because this is a physical phenomenon of LCD displays, not a bug within macOS. Your mac is doing everything fine but I believe that your monitor needs some time to "refresh" its pixels. So if you had another external monitor and swap it with the current one when you are experiencing this issue, it shouldn't happen in the other monitor

Of course, that makes perfect sense.

 

[mcnuggetswithcheese]

It's a used display so perhaps it has been heavily used in the past.

Ah, this might be why.