Sigma 100-300 F4 D800 Anyone?
I don't have the D800 so can't speak to that, but I do have the Sigma 100-300 f/4 and it is a fairly decent lens. I would never think of calling it a lightweight hiking lens though. You owe it to youself to try to find one for a hands on test. It is a large lens that makes the Nikon 70-200 f/2.8 look small.