Note to self: Testing N.T.'s lens -- sigma 50-150 f/2.8. I shot about ten minutes of the second period.

Slight back focus, slower AF than the canon 70-200 f/2.8 IS, even with center point AF. I recommend micro-calibration for that lens for the back focus.

I switched lenses after a few minutes and noticed a huge difference in AF speed and hit rate increased. I think after my editing, most of my keeper frames were form the 70-200.