Could someone explain how wireless flash systems work, what equipment is needed to set one up, etc. A friend sent me a link to a device that you can attach to any flash to make it a slave but I had thought you needed another flash that could be set up as Commander (or the in-camera flash if the cam supports it) that would trip the flash. I know wireless systems suffer from the problem that any random Schmoe with a P&S can turn on the flash and then trigger the remote flash. Does that mean a Commander isn't needed or does the Commander use a pre-flash to set-up the remote before it actually fires it??? I know the SB-800 can trigger the SB-600/800 remotely but would devices like the one linked above make it possible to trip ANY flash with any other flash?