Slightly off topic but I was with a guy only last week who was shooting birds with a Sigma 135-400 f5.6 lens and I was using a Canon 400mm f5.6 L. My lens was focusing in a fraction of a second every time but the sigma was forever hunting for focus and sometimes it could not obtain AF at all - this was shooting exactly the same bird at the same time in the same light at the same focal length.
|