I know that you are using a tripod. Last year, when the Occupy fill-in-the-blank stuff was popular, I photographed a meeting with a Pentax 645 and Delta 3200. I went wide open with f/2.8, and metered manually. My exposure was 1/2 second, and I had to wait until people weren't moving so much. Otherwise limbs and heads disappeared.
Originally Posted by RattyMouse
Anyways, set your camera to M for manual, set the lens for wide, and set everything manually. Now you are set to have fun!