Have a question:
is this same as
i know the second link says OS HSM and first link doesnt, but its the same price
Sigma removed the OS from many of their Sony/Minolta-mount lenses including this one. So there are two versions. Many vendors are failing to remove the "OS" from the listing (even though the manufacturer's part number has changed) and shipping non-OS versions to people who are expecting the older OS version.
I managed to get the OS model from Henry's in Canada (in fact, they shipped it to my store twice so there is probably another copy in their inventory) but it took a while for them to find it.
would AF on the first one be compatible with my a57?
They'll both work with the A57.