This was taken on the Canon EF 70-300mm f/4-5.6 L IS USM mounted on a 7D. I dropped the shutter speed to 1/80 second and panned as smoothly as I could to keep the car sharp but blur the background. (A few years ago I went to a track day and used a fast shutter speed - all the cars looked parked!)
I set the stabiliser to mode 2 which means it will offer stabilisation in one direction, but won't interfere with the panning.
I had more 'keepers' when I upped the shutter speed to 1/125, but I like the amount of blur I got at 1/80.
Jeremy Webb, Rockingham, 7th October 2012:
Canon EOS 7D, f/16 @ 300 mm, 1/80, ISO 100, No Flash