The key with this lens or the 50mm1.2L is to reverse what we were tough in school, compose first, move the focusing point to the eye so you know you get good focus, do not move at all and ask your subject not to move at all either then take the shot; 99.9% of the times you will get very sharp photos. You might have to micro adjust it to some cameras, take the time is worth i!
Great reviews. Where can we rent L series lens? I have a Canon 70D and want to try out some L series lens before I buy any. They are very expensive and I better start saving some money.