While a fine grain master appears over-exposed and dark, it contains all of the information in the original negative, compressed into the toe and straight-line portion of the H&D curve via exposure and chemical processing. The image is uncompressed when the duplicate negative is made from the element and the tonal range expanded up into the top straight-line and shoulder portion of the H&D curve.
In theory, it should be possible to multiply the gamma of each element to arrive back at the original values of the image (unity or 1) at the end of the reproduction chain. In practice, this is problematic for a number of reasons, including a light scatter in projection which results in a flat, muddy image.
By way of illustration, to obtain a proper duplicate negative from a fine grain, the reproduction chain might resemble the following: A .65 original negative is processed to a 1.60 gamma fine grain, and from that to a .65 duplicate negative, resulting in a .676 gamma duplicate negative. The resulting element can be fine-tuned up or down with push or pull processing. Of course, the example is simplified and makes no provision for the method used to copy the elements or any of the other variables that would need to be considered. The calculation also becomes problematic when film of an unknown processing gamma or elements that are already at the suggested projection gamma are copied. Knowledge and experience would be required to manipulate the copying chain to minimize artifacts.