Stephen Lewis , Aug 07, 2010; 10:35 a.m.
IMHO you're better off using the old technique of predictive focus, where you forget autofocus, determine focus at a spot you expect the birds to fly into, pan them until they reach that spot and then snap the shot. To improve sharpness, in any case, you might consider using a tripod with a gimbal mount (various ones out there, but the Wimberley Sidekick is a popular example). On the Nikon end, you might also consider using some of the older manual focus long lenses...some of them are relatively inexpensive compared to their AF cousins, and their sharpness is quite good. For years I used an old beat up (cosmetically) 300/2.8 which had been discarded by a Newsweek photographer, coupled it with a 1.4x and/or 2x teleconverter, and it worked great (but because of size/weight) always needed a tripod. These days I typically use a Leica 400/6.3 Telyt lens modified to interchangeably fit and infinity focus on all of my cameras (Nikon, Canon, Leica & Sigma) for nature work. For a fun project and hand-held work, I'm presently converting an old Spiratone 400/6.3 for use on all my cameras as well. Central area focus is fine as is contrast, but the edges start to go unsharp at large apertures.