This is a theoretical proposition that might make enlarging to lith film or sheet film really easy. I'm interested in the possibility of making enlarged negs from slide film, or enlarged positives from negatives. Or you could make enlarged separation negatives (for tri-color gum for instance, carbon or DCG-dye-transfer) from color negatives by copying those with a slide-copier setup onto 35mm b&w film, with the appropriate filters, and then projecting those. Ok... Let's say you enlarge your image onto a gray card and meter the gray card, or alternatively, take incident readings of the projected light and then tell your meter that you are shooting at f/1. Would this not give you the correct exposure time?