TWI by Dustin Abbott said:
Big question - other than the focus being perhaps a hair off, how fast and, most importantly, how accurate do you feel the focus is?
Focus is fast. Not quite as fast as the Canon 400 f2.8 II. But its pretty fast. Fast enough for sports. As to the accuracy, not ready to put a stamp on it yet due to the back focus. I had some misses. Not an exceptional number of misses for a softball game. Some that surprised me were the longer shots. For instance shooting an outfielder with center focus, I caught the fence more often than I thought I would.
Update: I just spent some time tweaking the focus with the doc. I reset the 1Dx micro back to 0. I eventually worked my way up to a -15 setting on over 100'+. At that setting it is sharp! I then started working on the 120, 150 and 200 mm settings. I did not have time to put on the 5DIII and test it with the updates. I'll do a full review soon.
Suggestion, if you buy this lens, get the dock. Not sure if my situation is typical, but without it, I'd be calling Sigma or considering returning it.
-Mike