I'm pretty much guessing when I shoot with my flashes. I have a decent idea what power I should set my 580EX to, and a decent idea what my shutter/iso/apperature should be and then do a few tests and generally get it. But it's all guess work. I dont really understand the concept of aperture with a flash. I understand power and look at it that way - 1/1 is full power and then we go down from there. Cool. Lights too harsh, k ill bring it down. I'm kind of confused about my vivitar 285 though - the settings on the wheel... I dont have it in front of me but f stop numbers right? Sooo which is 'highest' and which is 'lowest' in terms of power of the light? Also -- the general rule is meter for the background then bring it two stops down and bring in the flash. Do i just set the flash to the f stop I metered to and adjust from there if needed? I just need to ramble about off camera flash for a minute i thikn. I'm pretty much happy with my results but I want to get it down so I dont have to fuss around when people are actually paying me.