Tokina 16-28, will a sharp one STAY sharp?
I've currently got one on loan from a friend who has done many things to this lens, including I think dropping it. The lens is still sharp. The only issue I'd say is that the focus ring is so loose and easy to turn that it would be very easy to un-focus it by accident if not held properly.
I'm certainly contemplating buying one.
My personal issue with the lens design (apart from above focus ring issue) is that to change from auto/manual focus you have to retract the focus ring rather than move a switch like on Canon etc. I'm guessing that this is a mechanical disengagement rather than electrically switching.
That part concerns me.
However in a few short tests I do think this lens is the best performance/price wide zoom lens for full frame.
P.S. I think the looseness of the focus ring could probably be solved by fitting a silicon type band around it to provide friction. Besides I never used anything other than autofocus with my Sigma 8-16 on my crop frame so it may not ever be an issue if I get a brand new lens.