I tried to ask this before but I didnt phrase it well so trying again. The concepts of zoom and fstop on a flash confuses me. Do I meter the background, then go one f.stop down from that, then set the flashes 'f stop' to the original meter? So if the room is f 2.8 at 1/250 do I bring it down to f4 at 1/250, then what do i set the flash to? I keep my 580EX on manual. It goes 1/1 1/2 1/4 1/8 1/32, etc etc. How's that translate? Also, when spinning the dial on the power setting it stays on that setting for more than one 'click'. IE i set it to 1/4 but there a few different settings within 1/4. What the heck are those? When I throw in a second and third light should I be having the slaves be set at a lower power? How much lower?