Cibachrome vs older Gasparcolor - how did they make Cibachrome color accurate?

[J 3]

There are a lot of very knowlegable people on this forum and I've always wondered about the older dye subtraction technologies vs cibachrome. Gasparcolor was an old color filmstock using dye subtraction. The technology was for prints and required each component color to be exposed with a seperation and the light wasn't the same color as that in the final print (blue light through the front created the magenta layer, blue light through the back created the cyan layer, and red light through the front created the yellow layer). They didn't have the technology at the time to make an emulsion sensitive to a color of light while containing a lot of the complement color, and also keep the light from cross contaminating an unintended layer.

But by the time of cibachrome they fixed this problem. Exposing to red light and developement causes a destruction of cyan dye in the appropriate layer and likewise. This means you can expose the bulk of the image in one shot without color seperations. They never fully solved the contrast problem but they did solve this one.

So does anyone know how did they manage to perform this trick? How is cibachrome able to be color correct when the older processes couldn't make this work.

 

[J 3]

P.S. Thinking about things I think the reason they had the red (cyan dye) layer by itself on the back of the film even though blue and green were stacked on thethe front with Gasparcolor was they didn't have scavenger layer technology to keep oxidized developer from the blue or green layer from migrating through layers (if they were stacked) to the red or vise versa causing cross contamination of the color information. The human eye is much more tolerant of blue-green mistakes than red-blue mistakes. I don't know if the layer technology is different for dye-destruction than it is for cromogenic but that part of Gasparcolor would make more sense if they didn't have the cross-talk prevention technology at the time.

It still doesn't quite explain why the couldn't produce a dye destruction film where the mapping wasn't completely dissimilar from input light when they could solve this problem later in though.

Maybe they didn't have the technology to make silver halide emulsions where the sensitizing dye is very tightly bound to the silver halide crystal? That would botch the chemistry when they went to mix the sensitized emulsion with the dye intended to be destroyed to form the image.