i would like to ask guys here , i satrted photography about 6 months ago and pretty much ok with my camera shooting with regular ambient lighting and flash. i have a nikon D70 and sb600 . I am wondering if i wannna explore more of multiple lights off camera - probabl using manual mode . how do you guys measure how much lighting you need . i know there are formulas doing the math about distance , aperture and guide number - can these numbers also be had with the help of a light meter?