I'm trying to figure out a way to reliably preflash film in camera. My basic idea is to double expose the film by shooting a grey card first. I found some EV>lux and EV>foot candle conversion tables in my sekonic light meter manual so I was thinking that if I could figure out how long i need to expose a given film at a given EV value to achieve various film densities then i could preflash the film to say 10%, 20%, 30% etc in any given lighting conditions. I've been looking at the data sheet for fuji pro 160s and am not completely sure how to interpret some of the charts, or even sure if they are exactly what I need. You guys have any ideas?