The dark side, whats that then. Only joking. So it has a motor built in for autofocus, right?
The dark side, whats that then.
will only autofocus if lens has HSM(hypersonicmotor) for D40/40x/60
if you need auto focus there's a 50-500 and a 150-500.
http://www.sigma-imaging-uk.com/lenses/index.htm