Color Separation negatives

I'm going to try taking color separation negatives from life using instructions in an old Photo Lab Index (the big red book). It gives factors for each tricolor filter and says these factors are for Agfa Isopan, and that factors vary for different films. Would most modern films respond in the same way that I would not need to adjust the exposures? I'm using #s 25, 58, and 47 filters.

I also was looking into the Kodachrome process of the 1920's as an inspiration. That process was a 2 color separation, using red and blue green filters. I was wondering if anyone knew what filters would work to create the appropriate color separation.

I was going to take 4x5 film and use the separations to make color gum prints so I was thinking the Kodachrome 2 color might be easier to start with and perfect my technique.

Exposure varied by film, light source and printing inks/dyes, developement varied by filter used, good luck with it. William Mortensen was working on a 2 color gum process, try a Goggle search, his research may be out there.

You can make 3 color prints via Carbon or Bromoil printing as well as dye transfer, and you can make Kodachrome like transparencies by developing separation positives in 3 Kodachrome style color developers. There are many routes to full color images.

PE

Radioiron said:

Would most modern films respond in the same way that I would not need to adjust the exposures? I'm using #s 25, 58, and 47 filters.

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You could test, measuring the densities each produces for white subjects (should, of course, be the same through each filter).

I also was looking into the Kodachrome process of the 1920's as an inspiration. That process was a 2 color separation, using red and blue green filters. I was wondering if anyone knew what filters would work to create the appropriate color separation.

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For daylight, Wratten 28 (red) and 40A (green).
For tungsten, Wratten 28 (red) and 40 (green).

For projection, Wratten 23B and 69.

Not sure that these are all still available.

"For daylight, Wratten 28 (red) and 40A (green).
For tungsten, Wratten 28 (red) and 40 (green).

For projection, Wratten 23B and 69.

Not sure that these are all still available."

I believe they are still available as gels.

There was never a two-color Kodachrome process. There was a two-color Technicolor process, which shot two B&W negatives in the camera, and then made release prints using (essentially) dye-transfer in two colors.

I believe that there was an early 2 color Kodachrome. This was discussed elsewhere, regarding the early work of Man and God.

PE

John Shriver said:

There was never a two-color Kodachrome process.

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Yes, there was. The one and only original Kodachrome.

It was a two colour assembly meant for projection, invented by John Capstaff.

The name of that process - Kodachrome - was later reused, because when their time (and funding) ran out, Mannes and Godowsky, instead of being able to deliver the promised three colour process, proposed a two colour process.
Only in the nick of time did they get the promised three colour process to work.
So that became the second (!) coming of Kodachrome.

But we almost had not just one, but even two two-colour Kodachromes!

Kodak used to publish a very good little booklet called "Color Separation and Masking." It was still in print up to a few years ago, so you may be able to find a copy. Most texts recommend making exposures that will render a gray card the same for all the color separations. You must also be careful to develop for the same contrast in each separation. Kodak recommended including a paper gray scale in the subject when it was photographed or, if that was impossible, including a step tablet beside the transparency when making the separation exposure. Generally, a film with a long straight line section to the characteristic curve was used. (Kodak Super-XX, Kodak Separation Negative Film Type 1, and Ansco Isopan were recommended. I've seen TMax 100 recommended for modern work.) For direct separation work, Kodak recommended using Wratten No. 25, No. 61, and No. 47 for the red, green, and blue filters, respectively. When working from transparencies, sharper cutting red and blue filters (No. 29 and No. 47B) were recommended. A fairly early reference (1947 PLI) recommended that the exposure ratios for photoflood illumination be red = 1.0, green = 1.0, blue = 1.1 for Super-XX tray developed 6, 6, and 8.5 minutes, respectively, in DK50.

Two color work was done a quite a bit in the 1930s, especially for projection. In some cases, an emulsion was coated on each side of a thin base to simplify handling. I've seen references to both Kodachrome and Technicolor using the two color method, at least for experiments. As I recall, the original Kodacolor print film (think late 1930s) was a two color process. If you have access to two slide projectors and maybe a dimmer for one of them, you can do some interesting experiments with two color additive color photography. You can also try contact printing two color separation negatives onto color paper.

Thanks for the help.
I have a book of polyester filters from Rosco that I bought a few years ago for a science project and have been finding the equivalents of the wrattens from the spectreographs, but I'm having a hard time locating the transmission curves for the wratten filters.
I found a site last week that had info on all the filters, but I lost it. Does anyone know a page with data on them all or have a pdf file?

I don't have a current page, but Kodak had the transmission spectra of safelights and filters on their site somewhere. I never kept the URL because I do have the Kodak book on Wratten Filters and safelights. You might be able to pick up a copy of that publication somewhere.

I'm sorry I can't be more helpful. I will try to look up some information on the book which is here somewhere but not at my fingertips.

PE

I just searched Kodak and I couldn't find any sheet with the curves, it seems they've gotten rid of a lot of the useful info on their site.

Try "Kodak Wratten Filters for Scientific and Technical use", publication B3. It is a soft cover 5x7" book about 80 pages long with all of the spectra. You might find it among used books somewhere.

And, BTW, we used the WR 98, 99 and 70 for printing and sharp cut.

PE

Photo Engineer said:

Try "Kodak Wratten Filters for Scientific and Technical use", publication B3. It is a soft cover 5x7" book about 80 pages long with all of the spectra.

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I have this information in Kodak's Data Book of Applied Photography (Volume 1), Publication FT-6 Kodak 'Wratten' Filter Colour-Separation Sets.

There is a table of wavelength vs. percentage transmission for each filter and a couple of spectrophotometric absorption curves for sets of three filters (super-imposed).

If this is the information which is needed, let me know and I will scan it at work tomorrow.

Radioiron said:

I'm using #s 25, 58, and 47 filters.

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The first set of three in the document I have is also 25, 58 and 47 (47B actually).




Steve.

That would really be a help. Thanks