I have thought of that very thing; but, I cannot find an optical-quality, neutral-density filter that is graduated from center to edge anywhere on the planet. I've been asking about such a thing for years of everyone whom I think has any photographic experience. And having been at one time a freelance photojournalist, published in People Magazine, CBS 60 Minutes, Time Magazine, London Sun, Melbourne Times Herald, India Times and a host of countries totaling over 40, I know a lot of photographers.
If anyone here knows of such a filter, I sure would like to know where I can get one.
As for filtering the light source, granted, it would not have to be optical quality; but, I cannot figure out how to insert a home-made gelatin filter between that super-hot projection lamp and the film inside my Super8 projector without frying the filter and ruining the projector. Even if heat were not a problem, I cannot see how that could work.
I intend eventually to send these old Super8 films to a pro lab for conversion to digital. But, they are irreplaceable so I want as good a copy as I can make before shipment to ward off catastrophic loss in the event any of the films are lost.