I may not be expressing myself well but, if I understood your OP correctly, what I'm saying is relevant to your original question.
Originally Posted by stradibarrius
If you use a digital camera to asses a light meter, which you later use for metering negative type film, the opposing dynamics of the two systems will tend to work against each other and thus may be the cause of poor exposures.
Using a digital camera to asses meter readings for neg stock is like running and trying to touch the hand of someone who's running at you from the other direction. It's easier if the person is standing still and easier again if they're running alongside you.
To put it in a purely film context. When I used to shoot Polaroid (essentially a transparency material) to proof advertising images that were later to be shot on negative film, I'd use compensation factors to compensate for the opposing dynamics of the different materials. If I'd shot at the same exposure, it would have been wrong.