Firstly I am placing this here rather in Motorsports because it's about the lens, not the cars. I had the opportunity yesterday to go to Mosport to meet someone working on one of the race teams so used the trip to evaluate several lens & body combinations for an upcoming Vintage Racing weekend featuring a 40th Anniversary Reunion for Can-Am cars. Hopefully the weather will co-operate & I can find time to go, and thanks to my trip I know what to take. It's been 10 years since I shot race cars, and back then it was with an A 1 and manual focus Tokina 35-200 lens, so things have changed. I have worked in the automotive field since 1967, and for the last 22 years am self employed restoring Corvettes & other GM muscle cars so do know a bit about racing.
The weather wasn't perfect, but at least it didn't rain. The sky generally went from lightly hazed over with occasional sun burning through but as the afternoon went by the haze got heavier and looking down even a short straight a way looked like a very light fog was over the ground. This shoot was to try & test lenses, not technique, so shutter speeds were too high for the nice blurred backgrounds usually desired. I used AI Servo and continuous shooting mode for all of these samples, plus centre point AF which seems to have worked perfectly as long as I actually hit the shutter button while on the car. I had tried filling the frame with 2 or more cars but that put the AF between them and the results show that the AF locked onto the background, so for that kind of shot it looks like "one shot" and a re frame would be more successful. Keeper rate is quite good considering, so here are my samples, firstly low resolution files that the slideshow works well with, and then several downloadable full file shots. I tried to shoot as many different colours as I could, and everything is exactly as shot, no sharpening or post processing. I have even included a set of 3 shots that were from a single burst, but in general the camera didn't seem to like taking bursts maybe due to me not keeping the focus on the car. Shots are in Av mode and I limited my shooting to the f 8 to f 11 range, and wasn't looking for wide open samples since I really wouldn't shoot that way.
http://picasaweb.google.com/cicopo/Mosport40DSigma18200OSLens?authkey=RsmCpsdXW0U
According to my eyes it looks like the images are more than sharp enough to satisfy most who can't afford the more expensive L series zooms, but everyone is entitled to make their own decisions on how much they are willing to spend & what quality they demand. Your comments are welcomed, as well as any other questions re my samples.

