Having spent many years shooting Road Atlanta, I went to Willow Springs this weekend armed with a 300 F2.8L IS to have a little fun and learn the layout of the track. It was a lot of fun, though the heat was just brutal.
I mostly used a 7D mounted to the 300 (with and without a 1.4x TC III) and a 70-200 IS II on a 1D2N. I did swap the 1D onto the 300 later in the day. As far as I can tell both cameras performed pretty much identically in terms of focus tracking. I used spot focus on the 7D - center point or one point below center in order to get some of the sky. I felt that I had a bit of trouble with metering as the sun reflecting off of the ground was extremely bright. I should have shot in manual mode, but to be honest it was so hot and oppressive that I stuck to shutter priority for the sake of simplicity. My brain was getting cooked. 
I used a 24-70 F2.8L in the paddocks - I've been really happy with that lens, I got a sharp copy that's been a pleasure to use.
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Thanks for looking!








