quoteavid A. Goldfarb
Another possibility, which Mortenson and some of the Pictorialists used, and is really easy for most people who already do their own darkroom work, is to make paper interpositive and internegatives. One of the particular attractions of this method is that you can easily retouch the back of the interneg or interpositive on a light table using soft lead pencil or charcoal or a drafting pen for sharp lines, etc. Apply pencil to the interneg to push up highlights and to the interpos to deepen shadows. Neat, eh?[/quote]
You can also retouch negatives to build up density in thin highlights in much the same way, it's known as Dye Dodging.
You tape the original negative to an unexposed but cleared piece of film of the same size and using dyes, re touch the clear film in the thin highlights. With modern materials you have the choice of using magenta or blue dyes to help increase the contrast.