Quote Originally Posted by perminna View Post
Do I need to take something else than normal aperture + exposure time + film ISO into account? The aperture of the pinhole is f/207 so it's about 9.5 stops from f/8. Do I just extend the exposure times by 9.5 stops (if I meter at f/8) and get good results?
You should also take into account long exposure reciprocity. Short: The longer your exposure time gets the less sensitive your film is. Depending on the exposure time that can be another few stops, especially with Foma 100.

Here is an interesting read about Reciprocity failure: Click!