As you probably know, I am a big fan of small flashes. (*cough* Strobist *cough), but sometimes small flashes just don't have the juice to light up a scene. It may be a big place that needs tons of power or a huge light sucking modifier that eats up all the light from your strobe. (Try using the SB 900 on the westcott 2.15 meters octabank, that would be an interesting strobe challenge). So I do have one big 400WS flash. (Ok, just before you hit me with the "you call 400WS big?? ppffffhhh!", I'd say that it was big enough for me when I bought it, and it was I could afford.
So anyway, if you are in a studio this is no biggy. Plug the flash to the wall socket, dial up the power and you are good to go. But what if you are outside the studio. On the beach, park, moon? [Image by andyarmstrong]