When it comes to tripods for airshows I gave up on them in about 1980 or so, I was 16 or so at the time. I had been struggling with them for a number of years at that point. The problem with PiF is that you are going to need to pan through pretty close to 180 degrees. Even as a mildly fit 14 year old I had come to realise that moving that far round a tripod in 30 seconds or so was not the way to go. Back then of course we had no image stabilisation, and shooting at 400mm was usually a case of 1/500 and prop blur be buggered. I solved the problem when I got a shoulder stock mount for the camera. Being able to swing the camera about like a shotgun makes for really smooth panning, at least when the subject is predictable. The one I had back then was custom made, for those that know it was sold under the Dixons (then still big in photography, now part of Currys PC World) Prinz brand. Now I have one that I built from one of those cheap Amazon 16mm tube kits for video rigs.
I have now modified this with a wired remote that has had the single double press switch separated into two, a thumb button for AF and a front button for shutter. It kind of works, at least I don't accidentally fire the shutter rather than initiate AF, but it seems that the 50D is unwilling to fire without doing the AF stage. The switch box is mounted to the forward of the two handles.IMAGE LINK: https://flic.kr/p/21dBEkT 0002
by Alan Evans
, on FlickrIMAGE LINK: https://flic.kr/p/21dBDDT 0001
by Alan Evans
, on Flickr
This is now pretty close to ideal for me, about the only thing that might make it better is adding a power zoom function. That is mostly because of my health issues, I find having both hands on the handles all the time helpful, so could use some means of aiding zooming.
When it comes to the actual AF PiF, is pretty easy. Compared to BiF even the most erratic PiF are flying in pretty much a predictable direction as far as the AF system is concerned. The AI Servo AF of the 50D is pretty basic, so I just have it set to all points. The 50D all points starts on the center point, but will then track across all of the points if necessary. I also have it set so that Disabled if unable to focus is set. This stops the AF cycling if I drop the points off the aircraft, or some much closer ground feature passes in between. Nothing worse than the AF cycling to MFD in the middle of the pass.