Please post the exact specs of your machine.
If you search for "iMac Image Retention" you'll find that this is an unfortunate problem that is plaguing some of the 27-inch late 2012 iMacs.
Since it's not happening to everyone out there, I'm trying to see if this is only afflicting a certain combination of custom configurations.
Are you using an i7 processor?
Again, please post the exact specs of our iMac.
What other devices do you have connected to your iMac? I want to know everything there is about it. Do you have a second display connected?
From the looks of your forum interest and posts you're a fairly intelligent chap. Please lets remain so - this is an issue caused by faulty screen manufacture.
No matter what is connected to the logic board, what programs you have used or even sites you have been browsing will cause this issue.
I will make one leap - I bet it's LG displays just like the Retina Macbooks.
The graphics card is also not the culprit - if it were processing a different screen over an exisiting app, game whatever, then why on earth would it produce a faint - ghosted image so similar to polarisation of a panel?
This is the same issue MacBook Retina owners are/have faced.
The fact that LG have still not moved to fix this is poor.
Asking the OP machine spec will not be of any help unless we can some how ascertain the panel manufacturer, anyone a terminal junky?
What other devices do you have connected to your iMac? I want to know everything there is about it. Do you have a second display connected?
I use a scarlet 2i2 external soundcard. No second screen and a Logitech wireless mouse.
I don't think that my external accessories may affect the screen of my iMac?
I've set-up about 10 2012 27-inch for a client. Noticed on about 7 of them have Image Retention issues.
Theyre all the same model.
27-inch, 3.2Ghz i5, 1TB HDD, Base-model 27-inch.
Nothing even has to be open for the problem to arise. noticed on a idle machine, went to log out and the desktop was ghosted over the login window.
otherwise fantastic machines. terrible production quality from the display manufactures.
Apple is apparently claiming this as "normal". Dont buy that.
That kind of luck is crazy. I've had six 27" 2012 iMacs in my office at various times, and not a single one has had image retention.
This seems the most relevant place for me post this comment. What displays are the new iMacs using are they LG or Samsung?
They're all LG. Samsung doesn't make 27" IPS panels. Their 27" panels are MVA and PLS. Image retention is nothing new with the 27" iMacs. I have seen 2009 27" iMacs with terrible image retention. The interesting thing is that Dell has used the same 27" LG panels as Apple, and image retention doesn't seem to be an issue with them.
i dont care if no one believes me or not but ALL iMacs have SOME image retention some are worse than others. Like some of them you really need to look for it but they all have it, ive so far tested around 20-25 of them they all have them to a certain point.
They're all LG. Samsung doesn't make 27" IPS panels. Their 27" panels are MVA and PLS. Image retention is nothing new with the 27" iMacs. I have seen 2009 27" iMacs with terrible image retention. The interesting thing is that Dell has used the same 27" LG panels as Apple, and image retention doesn't seem to be an issue with them.
I want to echo this. I went through 4 units that all had image retention\persistence before giving up and asking for a full refund. I worked with an Executive Customer Support agent that finally told me after my 4th unit that ALL 2012 iMacs WILL show some level of image persistence because of the fact that they're using IPS displays. I'm not a display expert in any way so take that as you may. I'm just speaking from my experience and from what Apple is telling me. I know that some people are claiming to have perfect screens with no persistence issues but Apple stance seems to be that persistence will occur because it's inherent to IPS displays.
In my experience with the 4 units that I mentioned above it seemed like the IR would occur after the unit was on for a while. I think heat has something to do with it. Perhaps this new super thin redesign doesn't do as good of a job at dissipating the heat away from the display as other models or Dells offerings.
Willam make a video not screen recording but a recording of the iMac itself turn off screen savers and set the screen to never shut off go to a site with a white background like vimeo or something that has mostly white. Make that page half screen leave it there for 10 mins then go to choose a color for your background make it gray come back to this forum and show the video uncut and share it with us ill believe it when I see it. Like I said some will have worse than others but they ALL have this problem if you this you will find this out too. Now weather you don't want to look for it or not that's a whole other issue.
Your wish is my command. I took a video of this for about 13 minutes or so, recorded with the iMac at max brightness. No image retention. Feel free to watch the video. Note I've also done this for far, far longer in the past, using the grid-pattern test as well.
http://www.youtube.com/watch?v=06waD9kOrII&feature=youtu.be
*EDIT*
While the first video was uploading, I did the grid pattern test, too, for just under 10 minutes (I got bored). No image retention. A while ago I ran this image for almost an hour with no image retention.
http://youtu.be/vmnuW8-AOz0
This is the image I used:
http://www.marco.org/rmbp-irtest.html