Ahhh okay, interesting. So the 16mm prints were sourced from 35mm prints back in 1980. And now they’re used as color references. I guess this means that 16mm prints don’t have much color fading? Or, if they do, then it’s predictable and easily correctable by an algorithm?
Since the year 1982 there’s been a dramatic improvement of the stability of prints. So, while 16mm prints created after 1981 were sourced from notoriously unstable 35mm prints, these 35mm prints were still in good shape at the time, and as such their colors were preserved through the much more stable post-1981 16mm prints. So, once you have a 16mm scan with accurate colors, you can match the faded 35mm print to the 16mm in an HDR color space using the color matching tool, followed by a gamma correction, to bring the contrast back to 35mm levels.