Greyish Smudge marks behind the glass screen.

I often find that inviting your contact to tea works wonders (Earl Grey, of course). It's amazing how rarely they accept ... but in refusing they very often feel obliged to concede.

I share the same problem with my mid 2011 iMac 3.4Ghz i7. It was only 3.5 months old and already developing bad gray smudge on upper right of the screen. So I brought it in, and in two weeks they have my LCD replaced under warranty. And now after the same period of time, it's coming back.. Again .. in the same position!

I play games with my iMac quite often, maybe 7 8 hours/week. I ordered iMac with 6970M 2GB GPU, why wouldn't I play games with it? So dont blame me for "too much gaming" on this Mac. I simply use this iMac for what it was specced.

Definitely going to buy AppleCare for this, otherwise I'm screwed once I run out of warranty. I've already been screwed after spent $2400 on this iMac. I couldn't complain much further though, beside this notorious smudge display problem, my iMac runs fast, smooth, quiet, and perfect. But this smudge problem ruins all of the experience, and that's what all Apple about .. user experience.

Now let's discuss why did I pick an iMac?

1. Macbook Pro/Air is underpowered (as any laptop out there) computer. It's just slow, expensive for what it is (looks nice though), and I dont want to be crammed working on a laptop. Connect it to 27" Cinema Display wont help either. Slow is slow .. period. So yeah I killed the idea of having a laptop years ago. For mobile computing, iPhone or iPad works fine for me. Showing some works for client can be done easily on those, or I simply plug my HDD on their laptop. No biggie.

Simple physics man .. size does matter, bigger size means you can have much more power with a computer. I might sound conservative, but it's go big or go home for me.

2. Mac Mini .. well it's basically a headless Macbook Pro, same mobile CPU/iGPU/HDD .. still no.

3. MacPro .. now this looks big boy on the block, but let's see.. for what it is: outdated hardware, no refresh for a long long time from Apple, I have to say no. $2500 for lowest end MacPro and I still have to buy monitor means +$1000. Now if I had $3500 to burn, I wouldn't think twice to buy it. Unless the price tag already includes the 27" display... that would be tempting.

I know .. I know .. TL;DR .. in short, for a $2000++ Apple computer, surprisingly iMac have the best performance/price ratio among all Macintosh line today. It does compete with basic MacPro + monitor ($3500) with only $2500 display included (and we're talking about 27" WQHD display) .. Plus it has Thunderbolt now, great possibility for hardware expansions in the future .. so, who doesnt want that? It's really great on paper.

This smudged display problem simply *****, even after AppleCare I really have to bring it in regularly like a sick baby and have display replacement for like, next 3 years. After this, no more iMac for me. I'll bit the bullet and get a MacPro, and if somehow MacPro being discontinued (you know Apple love MacBook line and iOS now), I'd go Hackintosh.

Same problem here unfortunately is out of warranty. Today i was asked to pay €520 if i want the screen to be replaced. iMac 21.5 3.06Ghz late 2009 model. Bought it early 2010. WHAT A JOKE €520!!! Of course i will live with the smudge as it not that annoying.

Just brought mine in for the 2nd repair. This time they said they will replace the LCD but this is the last time since I put in a SSD and that voids the warranty. Ugh!

One interesting note, they said there were two part #s for the LCD screen. One was a newer one. I'm wondering if they have fixed this w/ the new LCD?

Well .. they told and promised me the same thing the first time I brought my iMac in.

They said that they will use newer kind of LCD for my replacement so that the problem will less likely re-occur, and BAM .. that's a total PR bulls. I still have the same problem after 3 4 months with this so called new type of LCD. Either they're lying, or the newer LCD still does not able to overcome the problem.

My analysis? It's a burned out LCD matrix, most likely happens on upper right corner since it's where your GPU heatsink is located. No easy fix, matrix is broken so you'll have to replace the whole display.

If you ever see a DSL modem hung on wall, after some months the wall on its back being blackened due to heat from the modem. Do you ever see that? Happens on many heated surfaces too. So that's what happened to the LCD matrix on your iMac. It's baked by GPU heatsink and burned out overtime.

How to solve? Keep replacing the display wont fix the problem permanently, it'll come back sooner or later. The cultprit is the GPU heatsink, you have to move it to another insignificant position (i.e the chin below) .. but that's impossible. So yeah, the very least you can do as a user is keep your GPU cool, don't play games on it, don't do anything GPU intensive, and the heatsink won't get heated. As the end result, the screen will be fine in a long time.

You know what's funny? If I'm not allowed to utilize my GPU power (It's a frickin 6970M .. decent for gaming and then some!), I could just buy a mere Macbook Pro/Air with lousy GPU for half the price of my iMac!! Now I paid A LOT supossedly to have this great spec and maximize its potential. So it's kinda stupid to not be able to use it.

Seems they are deleting stuff left right and centre.

SHOCKING - APPLE SHOULD BE ASHAMED OF THEMSELVES.

I came back from a 2 month vacation to find once my led cinema display had warmed up I had a bid grey splodge on the top right hand side of the screen maybe 6-7 in in diameter. I put this down to the display being off for two months and a little bit of condensation had got in. I put a hair dryer on the area for a few minutes and its seems to have rectified the problem for now... Maybe a different case from others but work a try and you wont invalidate any warranties that way 😉

Same problem here with my 2010 27" IMac. Grey smudges in upper right (mostly) and upper left corner. I got the BS line about candles, smoke, etc. Didn't argue too much b/c they agreed to replace the LCD free since I have remaining apple care warranty. But they said if it happens again, they WILL NOT replace the LCD again as they claim this issue is not supposed to be covered under apple care warranty. There is NO WAY this is a user / environment problem. It's a design flaw either from the sealing of the lcd assembly or the effect of CPU heat on said assembly. Don't bother mentioning this forum to the apple store employees, they just say they never heard of the issue and give u a blank look. They must be trained on what to say for certain problems. I just hope Apple fixes the design flaw because otherwise my machine is flawless and I love it just as much as my two iPhones and my IPad.

Hey guys, I found something! Apparently our "smudged display" is not exclusively pwned by iMac, or all-in-one PC. It is something common in LCD world.

Commonly it's called clouding, or MURA (Japanese, means unevenness). You can google "Mura LCD" and you'd be amazed knowing that your iMac is not alone in this. Basically anything that use LCD display (anything from HDTV, monitor, iMac, Cinema Display) induce the risk of this problem.

To sum things up, this Mura problem caused by stress applied to the LCD matrix (heat, mechanical) and yes, it is irreversible. Once you have this defect on your LCD, you'll have to replace it. I had a thought earlier that this smudge was caused by heat came from GPU/CPU heatsink behind. And yes it is. Continuous heat causes this problem.

So, things you can do to reduce smudge display or prolong your LCD life:

1. Ramp up your fan (yeah, smcfancontrol)! Stock fan speed is just not enough, the reason of iMac having so much of this problem is due to heat. LCD HDTV is not heated as much as iMac because it has so much less component inside, so it'll less likely happen on them (although it's still very very possible, remember it's still LCD).

But yeah, ramp up your fan a bit for normal usage, 30 - 50% from stock RPM should suffice.

2. Reduce gaming time, yeah yeah if you bought hi-end 27" iMac (like I did) you'd bang your head to the wall because it has a nice GPU, but really, limit your gaming time. Don't do it too long, 1 2 hours a day or 7 - 10hours a week top. It is for your own sake and your iMac longevity. You want to bang your $2000 computer, well suit yourself.

3. Make sure your iMac has enough ventilation and breathing room. Air circulation is important to keep your computer, and the display cooled.

With that said, I think it will be useless for us to sign up some p e t i t i o n regarding this problem. To be fair, it's not the Apple's fault either. It's just the nature of LCD itself. And all Apple should do is moving the heat source (heatsink mainly) to be not in behind LCD (i.e the chin). As long they keep the same design, this problem will come back to you, again .. and again .. and again.

I really hate LCD for a long long time now. I had a bad experience with 2 LCD HDTVs I owned earlier, it fails between 2 years! Now I only go Plasma for TV, if only iMac comes with plasma, CRT or LED option, well I won't take the LED LCD for sure. Real garbage display technology IMO, too much drawback induced for the thinness sake. 😀

Hi iSayuSay. Appreciate the thorough post, and I don't doubt that this problem has the potential to exist on all LCD's, but personally what I (and I think a lot of other folks on this thread) am experiencing with my iMac screen is not "clouding".

This has been my go-to link to best describe this problem (scroll half-way down for pics):

http://forums.macrumors.com/showthread.php?t=1101370&page=2

Or a close-up here of the real issue we are experiencing with our iMac's:

http://forums.macrumors.com/attachment.php?attachmentid=287668&d=1306956612

Whatever this fine material/dust is that accumulates between the LCD and backlight, that's what I believe is causing the smudges on my screen.

Again, not saying that clouding/mura doesn't exist; I've seen it myself on a friend's older LCD TV. But the fact that the person in the links above could take apart their machine, disassemble the display unit, and literally wipe away the "dust" (with some effort), leads me to believe this problem is not what you're describing in your post.

And, assuming that what I wrote above is true, then I think it is Apple's responsibility to address what I consider to be a material defect in at least some of their iMac's (ie, screens not properly/fully sealed, or whatever the culprit may be).

Hello BinaryMango. Thank you for your reply. Oh yes I'm aware of that thread you gave me. In fact I'm a member there with the very same nickname. I posted there too in the last page, I think 🙂

Some people eventually able to get rid of black spots by following Oggy's thorough guide, but a few people report otherwise too.

I think there are different types and causes which result the similar spotty/smudged/clouded LCD on iMac.

In my case I hardly believe it was a trapped dust. My iMac has this problem on upper right corner of the screen, and I game a lot on this computer for the first 3.5 months of posession (well it was new, you know how it is .. honeymoon! 😀 ) and then I had the display replaced once by Apple. It was clean and perfect again. Case closed! .. for a while

But I read it will come back again in many cases. So I arranged an experiment, this time I try to reduce the gaming time compared to before and ramp up the fan most of the time, within the same period (3 months or so) I can already see there are another smudges on almost exactly the same location as before, it's much less visible this time (now I conclude it because I dont heat the GPU as much as I used to).

That's why I thought .. the culprit is heat coming from behind. All kind of LCD will do the same when exposed to excessive heat. And because iMac design is to put computer machine behind the display, it happens in much accelerated pace compared to regular monitor, LCD TV etc.

I notice GPU heatsink can reach 80C when it's used for intensive gaming with the stock fans RPM, while CPU side relaxing at around 40C.

Ramping up the GPU fan to 3000rpm for gaming helps reduce the temp to 65-70C.

Well .. it's just my thought anyway. Thank you BinaryMango.

I suppose you have the same problem with iMac? How was that going? DId you follow the Oggy's guide or had Apple replace the LCD for you? And the most important question is ... does it come back in your case?

Same thing iun the Netherlands, there are a lot of folks here that have the "grey sport screen" issue.All of them seems to be iMac 27 inch. I have had 3 replacements in 2 years time. The last one was in septmeber. Last weel I called Apple Support 9I have Apple care) and expected the machnine now to be replaced. Eh, nog go. The lady from Apple told me that in fact I wasn't even eligible for a 4th replacement (but they were "willing" to make an exception for me....). They ivestigated the matter and she came up with the same ******** as pthers in this post decovered. It is a environmental problem..... Whena asking her to confirm this by mail she answered that this wasn't possible. I have no ideau yet how to address this issue properly.Perhaps some Twitter-noise will wake them up! Good luck everybody here.

When I got my first 27" iMac in mid/late 2010, I only got about 3 months use until the gray smudges appeared in the upper-right area of the screen. So I took it in to the Apple store near me and they replaced the screen no questions asked. (There's a much longer story here.. while replacing the screen they accidentally damaged my iMac's logic board and somehow screwed up the whole computer enough that they offered me a replacement, which I accepted. So instead of just getting the screen replaced, I have a whole new iMac and I'm a happy customer. Then, about 4-5 months later (this is now early/mid 2011) the gray smudges appear on my new screen as well. I also game on my iMac (Windows partition through Bootcamp) so I'm sure my temps are also getting fairly hot.

Maybe it is a matter of heat and not dust, or a combination of the two. I guess I'm just so blown away by Oggy's disassembly post and the literal "wiping away" of this.. stuff...

I am wondering why this hasn't gone to the media...anyone know an approximation of the numbers of people affected? I'm sure a story about apple ignoring their customers,the refusal to replace the machines of unwitting cutomers regardless of warranty and the whole issue with the design would make good headlines.....and corporations respond to such ...

i also played a lot of games when i first got my machine and the marks appeared within a few months, i note that my macair runs very hot when i game on it so i presume the imac does the same and the design makes it worse...