I'm trying to learn a bit more about using my flash (Canon 430EX), and I've been reading Understanding Flash Photography, by Bryan Peterson. In the book, he often says something like "I just entered my aperture and the flash told me the appropriate flash-to-subject distance ... so I set up my light stand at that distance and was good to go ..." or "I set up my flash and entered the distance to my subject ... the flash told me f/5.6 for a proper flash exposure ... ."
I (think I) understand that the distance for a proper flash exposure is a function of aperture, flash power, and ISO (and any ambient light I guess). My question is, can I manually set values for aperture, ISO, and flash power on the flash itself when it's off camera as a slave? I can only seem to set the power. And, based on that, my flash doesn't tell me the flash-to-subject range. It sounds like Peterson is able set all the variables right on his flash with his Nikon SB-900. Do higher end flashes (like the 580EX II maybe) allow for this -- assuming it's a model more comparable to Peterson's? Or am I just misinterpreting what he's saying?