Upload & Sell: On
However, my 400 f/2.8 IS MkI is a beautifully performing lens, and I'd be hard pressed to sign on the statement that my 400 II has better IQ, although it is just possible that my 400 II has a very slight sharpness edge which in practice has little consequence. In addition, both lenses have a very fast AF drive, just that they are tuned differently, therefore a direct comparison is not straightforward.
Peter, you lost me there.... I am referring to the difference in AF drive/tuning between the two versions of the lens - in what relation does it have to do with the IQ in a straightforward optical comparison?