I am looking for a good lens for sport photography. I can not afford the Canon 70-200 f/2.8 lenses. The research I have done on the Sigma 70-200 f/2.8 makes me wonder about the auto focus. I'm also not sure if I would be happy with the speed of a f/4 lens. Ishould mention that it will be used for fast-pitch softball and basketball. I know I'm limiting myself, but if I'm going to fork out $600-$800 for a lens, I want to be satisfied. Any advise would be appreciated.
Kevin



