Posted 16 August 2011 - 10:55 AM
I got yelled at, last movie I worked on, for bugging the DP too much about some emulsion batch discrepancies in the film he ordered.
"You don't even have to worry about emulsion batch differences anymore," one of the ACs told me.
Nevertheless, I tried very very hard to keep the few oddball cans we had of '07 confined to inserts, and locations with a short amount of screen time; this is with new film.
I'd recommend you get all old stock clip tested, and, if working with different batches, try as hard as you can not to mix an emulsion on a location, especially without shooting a grey card and Gretag/Macbeth color chart. If you shoot these charts for each location, properly illuminated by your key light of course and not washed out, you can as-closely-as-possible with film time out any discrepancies short of severe age fogging.
On neg. film, those RGB numbers you get, status M densitometer numbers translate so that roughly 0.17 or 17 points is equal to a camera F-stop, due to neg film's low contrast. The number of points over ideal that you are getting in base fog is roughly what I would try to overexpose to overcome age fog, but again, with matching it, you'll get contrast, shadow, highlight detail differences that could become objectionable.
Even with a skilled camera crew that actually knows this sh__, you may want to avoid the hassle of having them juggle different emulsion batches. Unless they have an "it'll be fine" attitude (ignorance is bliss, after all) it adds a lot of stress to production having to worry about running out of individual batches of film in addition to different stocks.