It's a APC lens but works great on the a850, with only a very slight vignetting at the outmost corners.
Think this will be a new favo lens, very nice. Just wish it had been of SSM type as the canon and Nikon variants.
Edit: Oh my... it is internal AF... i'm so stupid sometimes... :-/
A little noisy when AF going long way...
Haven't tested it thoroughly yet, only had it for a few hours... and just went out for a few shots.
Edit: After some time with it I just love it... on a FF camera count in the vignetting for distant shots, but for most macro shots it's hardly noticed...