Being a student of the zone system (had couple of semesters of it college and yeah I did all the tests) you don\'t over expose Ron but you base exposure on how much shadow detail you desire and control contrast through negative development times. So if you meter the high light and it\'s one stop to high to record detail you do an N-1 development to keep that highlight from going off the scale. If it\'s two stops to high you do an N-2 elopement time. Just a quick off the top of the head without actually doing the ASA test and the N+ and N- testing if you had found you normal development time for a certain developer and film was 68 degrees at 12 minutes and N-1 would be about (again without testing just off the top of the head) about 8min 30sec min. N-2 would about 7min 45sec . If the scene is to flat and the highlights need to be increased to get a full range N+1 on a 12 min dev time would be about 16min 45 sec. Shadows are full formed after 50% dev time so you are really controlling nights through extended and compacted dev times.
For this to work with roll film shoot the entire roll in the same light and you should be close. It\'s best to shoot the zone system with large format B&W film and process each sheet for the right dev time. I would save 14 sheets and hand process in trays (total darkness) 3 min presoak to keep the sheets from sticking together and just bottom to top of the stack agitation. I would save all of my normals until I got 14. The same with the N-1sn N+1s etc until I had 14 sheets of each.
This is WAY over simplified and basic but you get the drift.
Just wanted to add if it\'s roll film I would shoot the roll and if the light was flat and I would spot meter the room or scene before I started shooting and if it was a flat situation (not a lot of contrast I would just increase my negative dev times. If the scene was really contrasty I would beck off the dev time and use my experience to tell me by how much either way. Then fine tune with graded papers and burning/dodging and other techniques.
