>>4468337The longer the exposure, the more forgiving the times become. Say the correct exposure calls for 8s. If you accidently go to 15s, that's only +1 stops. If you undershoot and only go 4s, that's only -1 stop. Id play around on digital first for a day or two and then full send on film if you'd like. Make sure you factor in reciprocity if the film needs it.
