Thanks, DrDre! This is great stuff! Your results are excellent but, more important, the process subdues “personal perception” twiddling … to move the faded film back to specs (all things considered).
I suspect that other functions in my paint program (gamma, mid-tones, etc.) are wrong (that is, made for different purpose) but serviceable in proof-of-concepts. On this laptop, it appears my last picture “inexplicably” went bluish in the dark shadows of a “neutral color” bunker after application of “mid-tones” (contrast).
Are such “standard” functions in your process pipeline? Or would generalized functions, created to be more spectrum symmetrical, be more suited to this task? (I was thinking of testing such.)