There's only so much you can tell from a prototype lens mounted to a tripod at a trade show, but Sony's 500mm f/4 G SSM isn't just any lens. It's as huge as the $16,000+ hole it'll make in your bank balance, and even in the unfinished form shown off at CP+ looks to be quite the performer. The autofocus was impressively fast when mounted to an A77, and the lens should make an even better partner for the full-frame A900 successor that Sony confirmed today.