Capstaff's two-colour Kodachrome process.
Hello there everyone. As I spend my time on this part of the APUG forums, I generally spot quite a bit of interest in the now sadly discontinued Kodachrome film product together with the ghastly difficult K-14 process. I'm sure that most people recognise Kodachrome as the slide film made by Kodak invented in the mid thirties.
However, it might be interesting to note that the years leading up to the First World War, the word "Kodachrome" was in fact used to denote another product that used a 2 colour process. Simply states, you took two different negatives through filters (red and green) which after regular processing were bleached and dyed, one in a kind of bluish green (I want to say teal?) and the other in a kind of burnt orange colour. Afterwards, when you took these two positive transparencies together in registration on a light table, it made the appearance of a full colour photograph.
Now, one important thing to note is that since this is a two colour process involving essentially red and green, it fails to accurately reproduce blue, violet, magenta, and purple. However, it would serve to be useful for colour portaiture because of its ability to reproduce flesh tints, red, orange, green, gray, and black. The photographs themselves are surprisingly sharp and the colours themselves are accurate, rich and very true to life (at least for the spectrum they reproduce). Now, I have with the help of user "holmburgers" been able to find literature that addresses this process together with patents that might help someone get started if he or she would want to investigate further. I will provide the linkThis post over at New55 has all the pertinent links and gives some idea of the method. below.
One thing that is a bit frustrating is that it does not seem that the formulas for the dues that are used for the process have ever been publicised. One must give me pardon for my lack of knowledge in photographic chemistry, but I do not know how one would go about creating such dyes from scratch. I hoped that perhaps with help from others more knowledgeable than me, some light might be shed on that particular subject.
As I see it, this process does not seem particularly difficult to do granted one has access to the required materials. It does not seem to produce any more of a challenge than, say, toning a print or something in that manner. Some people might disagree, but I find that the Capstaff process might be interesting to pursue further, as it offers interesting results for anyone that successfully manages to reproduce it accurately.
Links for further literature:
-->The given post over at the New55 website has all the relevant links and gives some idea of the method together with some relevant information in the comment section, such as links to patents produced by Mr. Capstaff.
I did some work with T-Max 100 developed as a positive, one exposure with a red filter and another with green.
I then tried some dye mortanting recipes from Wall's book . Finding the right dyes and its concentration are the problem. I tried Rhodamine6G
and Malachite green I got some kind of results,but nothing close to reality.
This was going to be my plan B when they stop making color film
In a nutshell, Capstaff's Kodachrome worked by taking a silver-gelatin negative and exposing it to a tanning bleach, not unlike a carbro bleach or a dichromate bleach. This bleach reacts with the silver and hardens the gelatin in proximity, "tanning" the highlights (a.k.a. making the gelatin much harder and less soluble; cross-linking). Areas with less silver aren't tanned as much, i.e. the shadows.
This kind of image is known as a planographic matrix; an image in gelatin defined by differences in degree of tanning. This is what you create in bromoil, by the way.
Next step, dip these in the dye baths and voila; dye absorbs more freely into the untanned gelatin & less freely into the highly tanned areas.
What R Paul is describing is in fact a different process that relies on turning the silver into something like potassium iodide(?), which is a dye mordant and then dying the films with basic dyes (F.E. Ives pioneered this I believe, for his Kromskop process). Although dichromates are something of a mordant, they're washed out in 2-color Kodachrome and thus the staining mechanism is actually an interaction between dye & gelatin.
Capstaff's process requires acid dyes; which is actually a good thing. Basic dyes are incredibly vivid but relatively fugitive in terms of light stability. Acid dyes are generally less saturated but have very good long term stability; one reason why dye-transfer prints have such excellent dark keeping. The two dyes react with gelatin totally differently, another reason why we need acid dyes for this process. Acid dyes are also used in textile dying, meaning a great variety are commercially available.
Now, the tale of these dyes is quite interesting. It all goes back to an early dye-imbibition process called Pinatype which used planographic matrices exposed under positives to create matrices capable of absorbing and transfering dye to a final support. We can call these dyes "Pinatype dyes", and what (supposedly) makes them unique is that they preferentially stain untanned gelatin over tanned gelatin. J.S. Friedman wrote quite a bit about these dyes; indicating that knowing their names or class would be beneficial to everyone. In one journal there is actually quite an impassioned discourse on this topic (which I can find if anyone is interested).
So, historically these dyes are considered "secret", or at least were so in the late 40's.
But, all hope might not be lost. It's reasonable to assume that many dyes, in fact maybe all acid dyes (or reactive dyes, or direct dyes) have this property. A good place to begin is looking at dyes suitable for dye-transfer.
I should also note that there are some other ways to go about making the gelatin "matrix". One would be to use dichromated gelatin exposed to UV under a positive (not a negative; it makes sense if you think about it and the result is the same as a negative exposed to a tanning bleach). This would also create a planographic matrix. Lastly, and perhaps the easiest, would be to expose dichromated-gelatin under a negative and etch it with hot water (like in the carbon process), creating a relief matrix. A relief matrix is exactly what a dye-transfer matrix is, and the whole thing would consist of equally tanned gelatin that would dye up in proportion to its thickness (as opposed to its degree of tanning).
So in other words, we can completely eliminate this concern of "Pinatype dyes" (if such a thing really exists) and start working with relief matrices, of which an innumerable quantity of dyes will work with. Or we can investigate if it's possible to get these same dyes to act in a Pinatype or Capstaff fashion with planographic matrices.
I hope this is helpful, if not somewhat overwhelming. These Capstaff Kodachromes are really beautiful and worth pursuing, and I plan to start working on them in the fall.
Sure thing Umut,
Here are two excerpts from American Photo, Volume 34 (circa 1947 I believe). I can email anyone the complete series from this volume (inquire through PM please), but I'm only including the two relevant pages here. The second attachment, page 362, includes Friedman's plea for discovering suitable pinatype dyes.
Also, just noticed this reference,
"L. Lemaire (British Journal of Photography, Vol. 58 (1911), p. 969) made a study of the chemistry of the dyes which were suitable for the pinatype process."
Need to find this one too...
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As we say in Norway, I think I just had an aha-moment. I did not think of turning the process around like that. Just wonderful.
Originally Posted by holmburgers
So, one essentially creates a pigment-less carbon transfer glop solution to be poured on to a tissue, then sensitized, exposed and etched? What would the support tissue be made out of? Something clear like polyester? Or am I making incorrect conclusions here?
If you can't find it, I should be able to get a copy from the George Eastman House Museum Library.
Originally Posted by holmburgers
Land Effect from Scientific American 1959
I though you might be interested in this experiment. See http://www.aw3rd.us/scief/colorviz.htm
That looks like what I got when I tried it out. No true colors ,but shades of red-orange instead
Originally Posted by Prof_Pixel
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