I had a problem, that at least one other internet poster had, with infinity focus at 11mm. The problem was that the "hard" stop on the focusing ring (which went slightly beyond infinity) wasn't far enough to get focus much past about ten feet when using 11mm. (There was no problem with infinity focus by even 12 or 13mm, and by 16mm, infinity focus was right at the infinity mark--so clearly the lens focuses slightly differently at each focal length.) I was able to move the "hard" stop on the focusing ring slightly (even further beyond the infinity mark) by loosening two screws under the rubber that surrounds the focusing ring (and under black tape that was under the rubber), moving the ring slightly, and then re-tightening the screws. It didn't wholly cure the problem, but it is now tolerable at f/2.8 and 11mm (where it wasn't before) and DOF renders the remaining issue moot by f/ 5.6. 12 - 16mm, as before, are just fine.