Backlight bleeding problem "unknown"

I think it's likely your viewing angle. Make sure the center of the screen is in line with your eyes looking straight ahead and try to have at least two feet between you and the screen.

I actually raised my iMac from the table to achieve the right height and the bright corner effect pretty much disappeared. You just have to factor in that this is a big screen and being too close or at too steep an angle, you'd actually be looking at the inward edge of the screen where the backlight is being reflected.

There are certainly some units that have bad screens so please don't flame me. I'm not saying that what I just suggested will fix all backlight bleeding problems...

Enjoy your iMac, OP, just as I am with mine.

 

Backlight bleed

The issue you're talking about is called backlight bleed and unfortunately is quite common with these displays. I too have it in the bottom corners, it's a little worse on the left hand side. Anyaway even you're looking at the screen from far away you can still notice this on dark backgrounds. I first noticed it when I opened front row. Anyway, I don't notice it when I do general computing so it doesn't bother me too much.

 

Backlight leak gone?

So how did this story end. Did you go for a replacement, or did you stick with the leaky screen.
I have the same problem, even after replacing it once (dec 2011).

Want to know if it is worth the trouble - numerous other things seem to be a problem too (black spots, dust, etc etc), and I think the more it goes in for repair the larger the chance I will have some other problems...

 

Same as what Semimorphus said. I had mine replaced in Dec 2010 due to 3 issues (DVD drive, yellow tinge and bleeding). If I look for it, the bleeding is there. I hardly notice it during normal use.

 

I think you are talking about the so called "IPS glow". I doubt they will exchange a computer based on that, this is a known limitation of the technology. Take any other computer monitor - I bet you will find much more irregularities/bleeding/color shifting issues that your iMac has. The question is whether you are content with the display quality or not. If no, try to return it, if yes: why look for problems? If you look for them, you will surely find them.

 

Backlight bleeding

Well actually I didn't go looking for it, which is part of the problem. I noticed it while working on photos - I couldn't see the corner of the photo at all, while editing. I noticed I was leaning 5 inches to the right of the edge of the screen and was thinking this is crazy! I should be able to see the corners of the screen in a dark image without practically falling out of my chair.
If I had gone looking for it, I would have found it on time and be able to change it. Now I am stuck with taking it in "for repair" and I just don't know what other risks there are. It is highly unlikely that it improves the quality of the build if it is taken apart several times. The technicians are only humans after all.

So I am still not sure what to do. Edit photos in the middle of the screen when they are very dark and put up with it (and ignore the white corners when the screen is locked) or keep changing it until I get lucky...

This was really unexpected. Never occurred to me that my 24" Benq would have less annoying irregularities than the imac screen. (Of course the colors etc are way better on the imac I assume, but the Benq has caught me of guard like this).

 

I just noticed that I was replying to the OP, who posted the question two years ago — that's embarrassing What you describe really seems to the a problem and I am sure Apple will replace your screen and do everything to provide you with a reasonable working machine. Here in Europe they will also usually do a pick-up service, so you don't have to bring it anywhere (no idea if it also applies to your area).