We found this independent video on You Tube, showing how Washington DC photographer John Harrington uses all sorts of carts, and explains the differences. John has the inside track, having taken photos of Bush, Obama, Steven Tyler, Aretha, and members of congress, just for starters. We don’t think this video is intended to be a contest but, as long as we’re watching, we like the vibe. How does RocknRoller stack up? You be the judge.