I'm not sure if this is normal or not. I just tested my brand new iMac 21.5 Take a look at the lower right hand corner. Do you see any problem??? Or maybe just my eyes are too sensitive. There is also a problem of back lighting. Take a look it. That's unacceptable. If anyone of you have 2012 iMac, I suggest you to test the display first as you have probably paid a lot of money for it.