Here is an example of how sharp the images came out, straight outta the camera with no post just a severe crop to reduce file size. More CA than a fixed 400 and not as sharp, but the trade off when it comes to framing multiple shots for different perspectives as the object passes by imo is worth it. I could tell by the shutter releases (or lack of them) from the people with fixed 300s and 400s their working distance was small, when i had the full range from 100-400 to aquire AF and framing while rapping off pics as quick as the buffer could dump to the MD, the looks i got.
Checkout my series on the Talon, although they left alot of shots out of the series you get the idea.
http://www.londonairshow.com/gallery.htmlAs fer AV and wheel spin, not when the object is fast say 60mph, you'd need a hard corner or hairpin for panning to work well, Shutter was 1/1000 and ISO 200, anything slower the pic was blurred.
Slower objects somewhat better, say 20-30 mph.
But for tracking and aquiring AF on a needle within a stack of needles with a high abstract background to confise the AF the range of the lens is superb.
ISO 400, 1/250, not bad for a F4.5 lens on a heavily overcast day with dim light.
Static objects @400mm the lens is tack sharp, this one is anyhoo. ISO 400
The lens is basically my prime and barely comes off the camera, can travel light to shows or whatever with no need for a mono or tripod just two Toplader bags. I switch out lenses all the time now in the field while standing up, have you tried the Sensor Swipes yet? They rock!
http://www.pbase.com/copperhill/ccd_cleaningI'd take a lens from your local store out for a test drive, see for yourself, some are slightly sharper than others.
cheers...