Correcting 1950 Ektacrhome or possibly or Anscochrome slides

Am currently doing high quality digitizing of hundreds of photos, collected from dozens of sources, for a forthcoming book. These are everything from monochrome prints from glass plate negatives (1910 era) to digital images taken last week.

Among these photos are some taken in 1950 on either Ektachrome or Anscochrome film--the mount is plain paper, and it is more than my life is worth to dismount them!

Not surprisingly, they have developed a very strong red cast (really a lot more than a cast!). Red snow, red pavement,light pinkish sky, etc.. Unfortunately, or maybe fortunately, the subject matter is a basically one of those colours between orange and red, or at least I think that is what it is supposed to be--I do not have a proper reference for it. BTW masking of the sky is pretty much out of the question -- streetcar trolley wires are a critical component of those photos.


Another problem, no idea if this is from the camera or if that is the way Anscochrome and/or Ektachrome deteriorate, is that they are heavily vignetted. The main subject matter is fine, but progressively into the four corners they get darker by as much as two or more f-stops I would think. Some heavy duty POM with an oval gradient fill sort of looked after that problem; however the colour breaks up very badly if the full amount required of lightness curve is applied, so the best correction so far still leaves the equivalent of about half an f-stop vignette.

I have managed to get the red out of the snow, and the overall colour cast pretty much out of it. The darker portions -- near blacks and either pavement or gravel, still come out reddish brown, not brown or wet asphalt colour. And the very light neutral tones (overcast skies, etc.) have a barely perceptible green tinge now (passable). Most of the correction was done using all the curves in L*a*b.

So, finally the question: has anyone developed a general procedure for dealing with late 1940s through early 1950s Ektachrome and/or Anscochrome? Would better results be attained through channel mixer perhaps? So far I have only encountered three slides, but as there are several hundred items I have not even looked at yet, and apparently hundreds more that I have not even received yet, I have no idea how many surprises await me!

EDIT: slight possibility those slides could be copy-slides on who knows what film; if so, copied prior to 1975, and the problems could either be the copy process, the source, or the copy film (or all!)

(BTW the book probably will not contain even a tenth of the material submitted; the publisher likes lots to choose from. But at least 50% of the material will be before 1950; coffee table history books are such fun!)