All going well, tomorrow UPS will deliver the newest member of my lens- family, the 70-200 f/4 USM L. I know this lens is notorious for backfocus problems especially on a 10D. Is there any reliable way for me to test if my newly acquiered lens is backfocussing? If that's the case, I assume BHPHOTO will fix it right? (I bought the USA- version). Is it just a matter of re- calibrating?