Can any transmition densitometer be used for reading b&w negative densities? I h ave made a series of exposures for zone I / film speed tests as laid out in A.A. 's "The Negative". The only lab on the island that has a densitometer, has an "R GB" unit. (what ever that means.) Will this RGB unit do what i need? I read something about an "RGB" densitometer somewhere, either here or in a book, and now I can't find the thread or article. I researched here, and skimmed back thr ough The Negative., but can't find RGB mentioned. As I'm new at this, (zone syst em, and Large format), all help is greatly appreceiated. dee