Fast Chamonix Porsche Replica

I have shot this car a few years ago at Brazilian GM test track. Back then I was using a Canon EOS 1D Mark II, a 17-40 f4 lenses and a polarized filter. Was in the truck riding side by side with another car, speed about 30 mph. Camera set 1/20 shutter speed, ISO 100 and f20. The secret here is to keep focus on all servo mode and shoot fast continuous. To get the perfect one, which means car frozen and blurry background, it can take form 20 to 200 frames, depending on how much you and/or the cars are shaking!