Hello. To start, I like both Canon and Nikon DSLR's. I've found an issue with the "focal" points. I purposely set "focus' using the center focal point for my action photography. Often times I find my subject blurred and objects "behind" in sharp focus. I generally shoot with a wide aperature to gain focus on the subject and a soft background. Much of the background in my images I don't want in-focus, ie. trailers, people, cars, etc. Is there a setting I'm missing? I use a 70-200 Sigma f/2.8 and a Canon 50mm f/1.4, of course the kit lens on the Canon 40D. Appreciate any help.