You're absolutely correct!
Originally Posted by Swellastic
The best support is this (Photographer Formulary's Subbed Melinex, a.k.a. polyester). Fixed out lith film, or LF film would also work well. Alternatively, you could do a carbon-like transfer to any surface, even glass.
I'm experimenting with pigmentless glop for dye-imbibition, and one thing that's improtant to add is an "extinction dye", in most cases tartrazine or FD&C Yellow 5 food coloring. This limits UV penetration, giving a nice thin relief image and subsequently washes out during the etch.
Thanks for posting the Land effect, that's fascinating. The strength of this 2-color approach is that some subjects look really good. Particularly flesh tones, which as you can imagine was probably the most important thing to render pleasantly. Also, wood, metal objects, hair, plants, etc.; basically anything you'd encounter indoors.
I can't help but think that these two color photographs are reminiscent of very warm tungsten lighting, or better yet fire light. And wouldn't it make sense that Capstaff and Eastman, indeed that whole generation of people, would be well accustomed to life without electric light? (certainly in their youth)
To talk a bit about the color theory behind it; the Capstaff process takes two exposure behind a red and a green filter and makes the separations teal and red-orange respectively. I'm curious how wide- or narrow-band these filters should be, but I assume that red 25 and green 58 would be a great place to start. Presumably the separation filters are narrow and the reproduction colors are rather wide in their spectral absorption, that is, they overlap into their adjacent secondaries to produce a more balanced (though inaccurate) palette. There are also a number of Wratten filters designated for "two color photography", and although some are likely intended for projection, some might be intended for making the separations.
* in case somebody missed this in the link above... http://image.eastmanhouse.org/files/GEH_1987_30_01.pdf