I consider myself fairly hardware savvy, but this has me flummoxed. Check out the faded ring around this iMac screen.
Yesterday it was fine. Now this. My initial thought was that the screen was delaminating or something, and light was leaking around the edges from the backlight. But it’s not.
Anybody else run into anything like this or have a magic fix before it gets taken in for repair?
Never seen anything like that myself. Just curious, have you run Apple Hardware Test?
Wow, that’s a new one to me too. Does the white border stick around when you log in, and when you do things like invoke the screen saver that would normally fill the screen? I’m guessing yes, and it sounds like a hardware failure, but it is a curious problem.
Yes, it was there regardless of what was on the screen. However, it gradually disappeared the longer the computer was on. The hardware test didn’t reveal any problems.
Never seen the like. Going away after time indicates a physical change, perhaps heat somewhere re-connecting a chip or cable. Hardware issue clearly, but very odd that it’s creeping in from the sides. Time was magnets kept CRT screens filled but obviously it’s not that. Very curious.
My sister had this problem a while back with an iPhone 5 or 5s, and it was because of a faulty screen. It might be the same thing, and you’ll need to take it in.
I once saw something similar, but it was with a TFT backlit screen; that should be IPS.
In our case it was a weird situation of high humidty and condensation; as soon as I disassembled it, I could see the moisture, and by the time I fired it up again sans enclosure, it worked fine. Used compressed air to dehumidify, reassembled; never came back.
What model (Axxxx) is that unit? If it’s 2010 era, it’s super easy to pull the glass off (purely magnetic) and see if you can detect anything, and maybe just run it without the glass for awhile and see if it self-heals.
Just asked around the group here; a peer loudly yelled ‘me too!’. LOL
He resolved it with a simple NVRAM reset; it was apparently something to do with the intentional blurring of images on the lock/login screen that was introduced in 10.12(?) getting “stuck”.
Another good test (after zapping NVRAM/PRAM) would be to boot from Recovery or a dedicated installer on a thumb drive.
Somehow missed your replies before. Thanks for the helpful info!
Did you find a resolution to your issue?
Any known resolution on this? I’m having the same issue. White border also seems to fade away with time. Very peculiar. NVRAM reset had no effect. Ran some diagnostics, but nothing out of the ordinary.
The problem gradually disappeared. I haven’t seen it since, unfortunately. So, no. Nothing to report. Glad it’s working, but I assume I’ll see more trouble at some point.
Another data point. NVRAM reset had no effect, this time on a MacBook. The white border appears occasionally, and shrinks and fades over time until it appears again.
Same here. This came up on Saturday, gradually disappeared over a period of about 3-4 hours. Hasn’t happened again.
A bit more info to add here just in case it’s useful to anyone.
My first (and so far only) occurrence of this was on Saturday, 12 Jan. Prior to this, I had last used the computer on Thursday afternoon. My work Thursday was interrupted, so I never shut down and it went to sleep on its own. When I woke it (Saturday morning, I worked on my Macbook inbetween though, not that lucky…) the new white border was there. This looked very much like the pic the OP posted. What you can’t see clearly on that pic though (and I’m not sure if Joseph had the same) is that the whole screen’s resolution wasn’t quite 100%. Even in the center of the screen things appeared to be a little lighter and more grainy than usual, this effect was worse the closer you got to the edges and faded into the border that you see in the pic.
We had a heavy electrical storm on Thursday evening, so my first thought was that there must have been some hardware damage, although in retrospect this is unlikely (electrical storm damage is usually a bit more all-or-nothing and other than the display everything seemed to be 100% normal).
I then proceeded to try and troubleshoot. Ran some diagnostics, reset NVRAM, restarted the computer several times using different permutations, tried booting into recovery mode (border was also there in recovery mode) etc. Nothing had any effect, but I noticed that the border (and the effect through the rest of the screen) was gradually disappearing. After about an hour the border was much smaller (interestingly it also started fading away from the edge, wish I had taken a pic of this, but at this point it was a faded border about 5mm from the edges and around 10mm thick). At this point I couldn’t really notice any quality issues in the center of the screen and the border was small enough that it really didn’t bother me that much anymore so I decided to get on with my life and ignore it while it disappears. After about 3-4 hours I couldn’t see any remnants of the issue anymore. To the naked eye, the display was perfect.
Since then I’ve experimented with (a) a prolonged shut down (>12 hours) period and start to see if it recurs (it did not) and (b) a prolonged sleep (>12 hours) period and wake up and see if it recurs (it did not). If an opportunity arises to test a longer sleep period, I’ll give that a shot too, although the ±36 hours sleep that it had prior to the first occurrence was unusual and would require a bit more interruption to my normal routine.
So unfortunately still no idea what the cause is, but mine appears to be fine now and if you’re having the same issue, hopefully yours will be too 
Here are another two observances, in case it helps anyone get to the bottom of this.
On a MacBook exhibiting the problem, the white border was not replicated when the MacBook was connected to an external display. Also, leaving the MacBook open seems to prevent the problem from appearing. (As reported above, the white border will gradually disappear as the Macintosh is used. Apparently leaving it open counts as use, even if it goes to sleep.)
I have the same problem which just occurred today. Did an NVRAM reset already did not work. So did anybody really determine the root cause and the solution to this except for waiting for it to disappear?
That is the identical edge blur effect found when in login screen mode on Sierra and High Sierra.
I had the same problem too, after a couple of hours switched on it solved by itself, and shadow was gone completely
I’m curious if anybody who has experienced this has had it recur or any further problems with the computer?
