justsomedude I have a question. How much does the 7D AF help you in capturing these shots(supposed you have a decent panning technique)?
I'm asking because with my 400d it is quite hard to get lots of in focus shots.. I usually put focus to manual and wait for the bike to come, else I may lose the shot..
Unfortunately, I don't think there is a straightforward answer to your question. But if I had to answer yes or no, I'd say "no"... the 7D's AF alone is not as big a factor as some people might think for these types of shots. However, there are other aspects of the 7D that do provide a little advantage over other camera bodies (I'll get to that later).
Don't get me wrong, the 7D AIservo AF is a help, but only a small factor in the grand scheme of shooting this kind of shot at 1/160th. The problem is at these slow shutter speeds (1/160th is "slow" for a racing motorcycle), the rider is moving and his fairings are vibrating/shaking violently due to wind/engine&road vibrations - so getting the entire bike/rider to be crisp is difficult (and sometimes just takes luck). I've tried shooting as low as 1/125 and 1/100, but my keeper rate becomes atrocious. 1/160th is about as slow as I can go (in corners) while getting a somewhat decent keeper rate, and getting the entire bike to be sharp. I have to bump the shutter speed up on main straights as the bike speeds are much higher.
All things considered, I'd say panning technique is priority #1 for shooting any type of shot like this, and always will be. Even when my focus is spot on, most of my throw-aways are due to camera shake (translation: operator error).
After panning technique, I think optics are the #2 consideration for panning shots, and they play a bigger role than camera body or AF type. Shooting with a fast lens with image stabilization (in a panning mode) can significantly increase keeper rates. Also, keep in mind that teleconverters - while giving you more reach - will actually compromise image quality. You also lose two stops of light with most TCs.
I shoot with a 70-200mm and use a 1.4x TC if I really have to. In a perfect world (where money grew on trees), I'd be shooting 300mm or 400mm f/2.8L IS lenses, like the two just featured on the home page
. Unfortunately, I don't have that kinda cash.
Lastly, there is definitely a point where camera body comes into play, but I don't think the AF processing is necessarily the key benefit. In my mind, the advantage to the 7D is the much larger pentaprism, which is actually larger than the 5D MKII's pentaprism (see pentaprism info in this review
). While processing certainly helps for tracking, it's of my opinion that this large pentaprism is a huge help to the 7D's AF system. Either way, I'd put the AF system as the lowest priority with respect to obtaining higher keeper rates for motorsports photography (that is, in a 400d to 7D comparison... obviously AF is a factor if we're comparing a 7D to a powershot!).
Remember, people have been taking these kinds of photos for years - long before digital AF came about... and somehow they were able to get tack sharp shots.
If you are able to get good crisp shots with pre-setting focus at a fixed distance, that means you're really dialing your panning technique down. Ultimately, if you upgrade to a higher-end camera, you'll be well ahead of the curve for handling the AF features that come with it.
I hope this helps!