Lately I've been having issues focusing properly, and I need help diagnosing the problem. I thought it was just me, but now I'm thinking my lens may be the culprit. I'm using a Canon XSi, and the problem-lens is a 50mm f/1.8. I am consistently missing the focus, both on auto and manual focus. It looks fine in the viewfinder, but then when I upload them, they are just off! I haven't had this problem with my other lens (Sigma 18-200mm f/3.5-6.3) and I thought that maybe this was due to the smaller aperture. Is my frustration making me jump to conclusions? How can I figure out where the problem lies? Oh, would pictures help?