Howdy, Is there a formula that would tell me the amount of light I need (preferably in WS) for any give film speed and apeture. For example (an extreme one), if I'm in a pitch black studio and want to expose an 8x10 sheet of tmx at f64 how much power would I need? I know at f64 I'm probably going to need mirrored solar collectors pointing down a skylight in the roof. Thanks for your help! John