Amateur photos of CBS color from 1951

[old_tv_nut]

Originally Posted by benman94

Quite faded toward a weird brown/magenta color.

So, it's definitely dye fading.

Originally Posted by benman94

I too think it would be odd to have a color film with fading in only a single layer, ...

Actually, this is exactly what happens - the fading is worse in the yellow dye and cyan dye, for example, leaving more magenta.

Originally Posted by benman94

Edit: I actually can think of a QC issue in manufacture that could cause what might LOOK like fading. If one of the three emulsions was mixed improperly, you could end up with a situation in which the record for that layer isn't "contrasty" enough compared to the other two. The processing would then continue normally, but the dye layer for the emulsion with the defect would be "weak" by comparison. The slide would look faded right out of the box, and any subsequent prints (like the Kotavachrome prints) would look the same. Now I wish I could go back to 1953 and see the slides when they were new.

Kodachrome quality control would never let such unbalanced film escape the factory. For professional versions, filter suggestions to get exact gray balance were provided.

Originally Posted by benman94

I can see Kodachrome being more likely to have layer-specific QC issues during development than say Ektachrome or Fujichrome with the integral dye couplers.

Exactly correct. Test strips would be run through the processor and measured to see which way things were drifting, and corrections would be made before variations exceeded accepted limits, to keep the process within certain specs.

Since the color-determining part of the reaction is in the Kodachrome developers and is different for each layer, the thing that makes most sense to cause a fading problem is that they changed the chemistry of the dye forming for one or more of the layers, not in the film, but in the processing, producing a less stable dye. In the case of all the other Ektachromes, Kodacolor, etc., the color-determining part is in the film and a common reactant is in the color developer. Therefore, the differences of composition of each dye is baked into the film rather than the developing solution. But, bad dyes could be created by either method. It's just very hard to find documentation of variants of Kodachrome chemistry, whereas Ektachrome and its cousins as well as color negative process shortcomings over the years are illustrated and bemoaned in books on process history and preservation. The loudest weeping and gnashing of teeth involves the Eastmacolor negative/print processes for movies that have often dark-faded to where restoration is nearly impossible.