Extremely weird "dead pixels" issue, which isn't.

[pavinder]

A really weird issue on my 27" iMac (bought 01/2014).

A couple of days ago I noticed what appears to be a couple of dead pixels almost right in the centre of the screen. These pixels remain black no matter what app or window I’m looking at. I figured it’s a hardware issue - dead pixels. I tried a number of "pixel repair" processes like jscreenfix.com but the pixels remained black.

But then I suddenly noticed that when I run my cursor over the pixels, the white border of the cursor arrow momentarily turns the pixels white. So basically the pixels are not dead. Weirder still, if I zoom my screen, the pixels don’t remain black, but the “spot” of black pixels expands, remaining in the same relative size and position to the zoomed area! It’s as if they’re a fixed part of the background. wtf!

I actually can’t get my head around what might be happening to cause this. What seemed a hardware issue now seems like it isn’t.

Any suggestions as to:

a) what’s actually happening? Why the pixels should be constantly black, but not when I run the cursor over them or zoom?
b) what I might do to fix the issue?

Thanks in advance.

 

[Fishrrman]

I realize this may seem like an overly simplistic suggestion, but:

If you have not shut down and then restarted the computer, why not give that a try?

 

[pavinder]

I'd tried that already and the problem had persisted.

But tonight I restarted 3 times in succession and strangely, the issue resolved itself. The simplest solution worked.

Thanks for suggesting it, Fishrrman.

 

[thekev]

a) what’s actually happening? Why the pixels should be constantly black, but not when I run the cursor over them or zoom?
b) what I might do to fix the issue?

Thanks in advance.

It's forced to redraw those areas at that time. Basically there's something with a high alpha value that overlaps that area, so it must be redrawn. I've seen the issue before, and I'm not sure whether it's a precursor for anything else. That aside I'm not sure what the pixel unstuck sites do. In cases of image persistence, one way to treat it was to use a solid bright color for a long period of time. It still wasn't entirely effective though.