Greyish Smudge marks behind the glass screen.

I also have had lcd replacements multiple times and replacement iMacs relative to the problem and guess what has returned? I'm a photographer as well: Mega-sheesh!!

I too have the same problem.

Details and photos here: http://discussions.apple.com/thread.jspa?threadID=2699434&tstart=0

Apple Customer Service called me yesterday and said that the issue is 'environmental'. Of course, they had no explanation of what they meant by environmental. I don't smoke. This iMac is in a clean, well ventilated, low traffic home-office room which only I use. There can't be a better environment to keep this in... and none of the other five or six PCs, UMPCs, Laptops and Sun Workstation I have in that room are affected.

How can I avoid having this issue from recurring??? I have lost my trust in the iMac 27 and Apple...

I have had my iMac (27 inch screen) for 7 months, and noticed the gray splotches behind my screen a few months ago. Took it to get the screen replaced and they claim that it is water damage. I said that was impossible, it's never been near anything wet and how in the world could that much liquid get inside. Of course that kind of thing isn't covered under the warranty. I was just so puzzled by this, and they also said that there was a lot of dust inside and that it must have been opened up by someone to get that much inside. The store I bought it at said it was brand new, never sold to another person before me, and that there is nothing they can do except charge me over a thousand dollars to replace the screen! Unbelievable that they are blaming me for this glitch. I thought that when I bought an apple computer for the first time, that I was going to get an incredibly quality machine, and this is the experience that I get for spending almost 2 thousand dollars of my hard-earned money. If apple doesn't want to take responsibility for their faulty screen then this will be that last product I buy from them. Too bad, because I actually liked some of the other aspects of the computer.

Mine has a VERY faint region in the top left corner.
From what i've read the causes are:
1. Leaving your iMac in "somewhat" direct sunlight. Having the sun hit only part of the screen every day, through shades and such...

2. Using your iMac's CPU and/or GPU a lot (games, rendering)! This causes NORMAL temperatures inside the case to heat up the LCD unequally.

BOTH cases involve the lcd being affected by heat in certain regions, over and over again. The heat isn't very high, but it's the unequal dilatation in the lcd panel itself that causes parts of the screen to degrade.
Apple's "thin" design aggravates this issue with the lcd panel. I think it's the lcd manufacturer that's to blame.

My personal opinion is that ALL iMac's will be affected in due time. The problem relies with the lcd panel itself, which seems VERY sensitive.

basilmir wrote:
My personal opinion is that ALL iMac's will be affected in due time. The problem relies with the lcd panel itself, which seems VERY sensitive.

I think you are spot on with your observation. I think so too. It's either a design fault or a manufacturing issue. But every iMac will have this occur over time... People just need to put a white wallpaper and a lot of them are going to get disappointed.

Since we are having big troubles in Serbia with same problem with display and we have dificulties in replacing displays, i am proposing a new topic where everyone would state model, s/n and country where the model is purchased, so that we gather more info on problem, and Apple can localize the problem since it is widely spread, at least here.

Apple iMac 21.5 late 2009 - W80025D7B9U, Serbia

Another one for the list. My 5 months old 21.5" iMac is now also showing these marks. For me this is not the first time I'm dealing with this problem. Over 5 years ago, my 20" iMac developed the same problem. The screen was changed twice, but the spots always came back eventually. As it was finally out of warranty, I began looking for a solution. There is still an old thread here from back then. An iMac owner from Spain opened up his machine and managed to identify the cause and fix it. Back then, these marks were caused by heat affecting a layer directly behind the rear display panel cover. I believe the technical term for that layer is "diffusor". After taking apart the panel, it was possible to simply wipe the spots away. I did this twice since my iMac was out a warranty anyway and then sold the machine. I cannot believe this is still a problem after so many generations of iMacs. Seems to be even more widespread than it was back then!
I would say heat is def. a potential cause for this. I realize some users affected by this are being told it is due to "environmental conditions". If that were the case, it would still be ridiculous. My iMac sits in an office along with 4 other monitors in close proximity, ranging from a super cheap Samsung to an ultra expensive Eizo. None of them are affected. So that would mean the iMac is sensitive to conditions that have no effect on any other displays? I would call that a serious flaw.

I think the problem is global, just another fact to it is the number of views for this topic >24k which indicates the fact that many people has it. Lot of them probably expirience it and are not aware or the size of smudges is small. Me personally can live with it, but i think its too much to pay very top dollar for such a machine 21-27" and get big headache by replacing and waiting for replacement od display usually with refurbished ones, since this is very easy resolvable problem at factory level. Also it is present since 3-4 years ago. There is a posibility Apple is still not aware of the size of this problem, and to be honest the problem is not possible to see in labs testing, since it is display manufacturer issue! My intention is to gather as much info about models/years affected so that someone can recognize and resolve the problem, since i really like and love Apple products 🙂

I am extremely upset by this thread. I'd planned on purchasing a 27" iMac to replace my 24" iMac, which is no longer covered by AppleCare because it is more than 3 years old.

I have always relied on AppleCare to fix costly problems -- Apple has replaced a total of 5 logic boards, 2 hard disks, and an optical drive under warranty on my various Macs over the years.

Now you're saying this problem with 27" iMacs and possibly other iMac models is relatively COMMON and NOT covered under AppleCare.

Maybe someone at Apple can explain why I should still consider buying that 27" iMac? At this point, I'd rather stick with something I know works -- at least for now.

I've got the issue and believe me, you really don't want to end up with one of these things.. I got one and made sure that it didnt have the yellow tinge issue which was the major problem at the time, but to my surprise i ended up with a much WORSE defect now..These grey patches ruin allll the experience to me..

Just done an OS update (not related) and while on the light screen as it reboots I noticed the grey patches about a 5th of the way in from the right-hand side. An area about the size of the palm of my hand. Looks like something splashed on the screen, but it is behind the glass. It is in a clean room that has stable temp. I really look after it.
In touch with Apple hopefully it will resolved.

Apple is insisting in "enviroment related" problem, BUT IT ISNT!! As soon as someone serious in Apple realize this, it would be better for Apple, since I know lot of professionals that are really dissapointed with this terrible ISSUE, not FEATURE.
FACTS: - almost ALL iMacs in last 3 years are affected, if you notice regions from which people report this problem, i suppose its not just one factory involved, but whole batch of LCD displays
- Apple is replacing displays with refurbished ones, confirmed to me by few technicians
- Its a serious problem, caused by bad isolation of difussors behing LCD display, where dust is formed

I urge Apple to investigate this problem and offer solution globaly, since we will have probably another *gate , this time "Displaygate"

I think the "environmental" explanation is simply wrong. Apple are, however, not the only company trying to blame this phenomenon on environmental factors. Just do a quick google search. You will find that this problem also affects certain LCD TVs. In some cases, the manufacturers refuse warranty repairs blaming the problem on environmental factors.

I simply do not see how anything could even get in there. Like I explained in my earlier post, I have successfully removed the smudges from an older iMac. So I know how the panels are constructed, and I doubt that changed much since then. The different layers are held together by a metal frame which completely covers all sides. Smoke or condensation could affect the front or rear of the panel, but it could never penetrate between the layers. It would have to pass through solid metal!

The diffuser has to be attached evenly to the liquid crystal layer. Even small irregularities would show as discoloration or a shadow. I believe the most logical explanation for our problem is heat affecting the diffuser from behind.

Same thing on my iMac 21'5 (august 2010, Russia), starts to appear in a 3-4 months. Lets keep this post updated until apple can provide affordable solution. Gonna show this post in customer service in case they refuse to repair.
Have to buy NEC now for reference )))

Its really AMAZING how the Apple let this INCREDIBLE stupid and anoying problem to exists.

Anyway here is couple of guys from Serbia that are repairing LCDs and explaining the problem, with difusors.

http://www.youtube.com/watch?v=zGOw2ufBYaU
http://www.youtube.com/watch?v=3hM5MqLD9TE