i've had this lens for about 7 months now and while i think it's a great lens, how to get consistent focus with the AF is still a mystery to me. i generally shoot around 1.8 to 2.2 so i know the dof is pretty shallow and perhaps that is part of the reason, but when i shoot, i generally use the center point, focus on the eyes or some part of the face and then reposition. sometimes it comes out the way i want, as in this example, other times, the focus seems to be on something else, not where I had intended (the water gun is in focus but i wanted the face to be). any advice on what i need to change in my methodology? thanks.