The cheap version! Two Quantaray MS-1 slaves on light stands, triggered by my Sunpak 383. Taken with my 17-40 lens quite a bit wider than the range of the on-camera flash. The Canon 580ex sends out a pre-flash so you couldn't use these slaves with it because they would fire before the actual flash. Using multiple flashes gives more dimension to your subjects. Since I don't really know what I'm doing I experiment a lot.