I took this picture of my wife driving an Indy Car at Chicagoland Speedway. She was doing just about 155mph. I wanted a blurred background to depict the speed appropriately.

I used a Nikon 800, a Nikon 200-400 zoom on a monopod, and panned with the car. Settings were ISO 100m at 1/100th and f/11.

It is one of my favorite shots because I know the driver, and I was trying very hard to get that blurred 'Speedway' sign in the background, which obviously took several attempts.