There are a few reasons to use a slow shutter speed on fast or slow moving objects.

In sports like Formula One it is a great technique to visualize the actual speed. If you use 1/1000 sec on a race car it almost looks like the car is parked on the track. If you pan the picture on a slow shutter speed the actual speed of the race is a lot more visible.

There was a second lightning bolt on the track with Jamaica’s Usain Bolt on Sunday night, Reuters photographer Kai Pfaffenbach. Below Kai talks about what it was like to keep up with the fastest man in the world.You can see Kai in action in this You Tube video.Despite setting up two remote cameras at the finish line myself, my colleague Michael Dalder (aka the remote king) set up six remotes and secured the best pictures of the finish line (above).Kai keeps up with Usain Bolt after the men’s 100 meters final at the world athletics championships at the Olympic stadium in Berlin August 16, 2009.  EPA/DPA Hannibal HanschkeI shot the finish line handheld on a 135mm Canon Mark3 and had an EOS5D Mk 2 with a 16-35mm ready on my lap. Bolt was running so fast on the outer curve that I decided to take a shortcut and cut the curve and catch up with him on the other side of the stadium, ahead of the other snappers. Running beside the world record holder, I was shooting on 1000 ISO at 1/800 sec f2.8.This was my tenth 100m final including Olympics and World Championships.  It definitely was the most exciting race. Of course I knew before the race that I would have to chase him but I didn’t expect him to be going that fast!