A few days ago I sold a guy a tele-converter I had, and after the transaction was completed we chatted for a while. He was telling me that the Nikon D7000 he had caused him all sorts of consternation with back focusing issues - ie the camera would tell the lens to focus behind the subject that the focus point is on. He eventually had to take it back to Nikon for a major warranty repair.
Quite coincidentally, that night some friends had asked us over for dinner. They had just bought their daughter a new D7000, and on close inspection, few shots were critically in focus. Remembering what the guy I had met earlier that day had said, I did an experiment between my D600 (which I had brought along) with the Sigma 35mm f1.4 at f1.4, and then swapped the lens over to the D7000. The D7000 focus was way out. In the crop of the shot below of the text on the wine bottle, it was completely unreadable on the D7000.
|Nikon D600 with Sigma 35mm f1.4 @ 1.4|
We then looked on the internet and found all sorts of articles on this issue. I then suggested that they take the camera back to where they bought it and request it be fixed under warranty. It was good to be able to diagnose this problem for them as they were wondering what was happening.