A couple months ago, when I got my Tokina ultra-wide, I couldn't help but notice the thing backfocusing regularly on my D80. Frustrated with the results, I sent it back to Tokina for calibration. They returned it, saying firmly that it was functioning within factory specifications. Well, unless I have it set at a large depth of field(f/8, for instance), it still backfocuses at 2.8. These results are from sports-related motions and so forth. Am I expecting too much from this lens in this context? Or is my camera just the piece that's screwing up?