"Cross-Processing", but not really... alternative processing techniques for E6 & C41

Discussion in 'Color: Film, Paper, and Chemistry' started by holmburgers, Apr 25, 2011.

  1. holmburgers

    holmburgers Member

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    Something I've wondered about is the ability to create a negative from an E6 film and a positive from a C-41 film.

    However, without using the wrong process to achieve it, which is what the traditional x-process is.

    As I understand it, the 1st developer in E6 is basically a black & white developer with some additional silver solvent in it; basically identical to the 1st developer in black & white reversal processing. Then, there is a bleach & re-exposure and the 2nd color coupling development.

    So, it seems an easy enough thing to just skip the 1st developer, go straight to the 2nd developer, yielding a negative.

    Alternatively, a C-41 film could be processed in a 1st developer that is nothing more than a b&w+AgX solvent dev'r, and then bleached, re-exposed and color coupling developed to yield a positive.

    Although, the positive wouldn't be suitable for direct viewing due to the integral masking, it would be finer grained by virtue of being reversal processed and have better color reproduction from the CC-masking. This might make for a superior scanning medium.... *cough *cough

    So, has anyone done this? How different are the color coupling developers for E6 and C41? If there is no difference, then I guess that basically this is exactly what normal cross-processing is and shame on me for not doing my homework. But assuming they're a bit different and optimized for the particular film, then superior "cross-processed" results might be achieved by this method.
     
  2. Mike Wilde

    Mike Wilde Member

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    The colour couplers in E-6 and C-41 are different. Hnece CD-3 and CD-4 as the normal developing agents. For c-41 the orange mask is used to shift the yellow, cyan and magenta layers to prevent them from crossing one another, and thus allow them to be separately filtered.

    There is a Kodak book called Copying and Duplicating that taught me a lot about this in the process of me working out the speed and filtration needed to use some out of date dupe films.

    Processing E-6 as a reversal will not have this mask present, and even superimposing a c-41 mask will not bring the colours into line to prevent crossed curves. Early colour neg films without masking (agfa I think) had this challenge. The mask also corrects for imperfect dye denities ie some of the red sensitive layer interacting with blue etc.

    The density of the different colour curves in C-41 must be matched to the sensitivity of the different colur layers of the paper in process RA-4.

    The density of the e-6 may not be offset; in fact I don't think it is at all, but I'm not up on the uniformity of vision sensitivity of human's optical channel relative to different light frequencies.

    Hope this gives you some thoughts to futher chew on.
     
  3. holmburgers

    holmburgers Member

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    Thanks Mike,

    You're right that E6 dev'd as a neg will have no masking. The mask in C41 is a function of the coupler's themselves being coloured reddish and yellow for the magenta & cyan layers. These offset the fact that these mag/cyan dyes are not "theoretically" ideal in their transmissions. Since the goal is a neg that's suitable for printing, it's appearance is of no importance, unlike a slide.

    So E6 as a negative would be more or less just interesting.. probably of little value.

    C41 as a positive though, could be great for the above stated reasons, and useful for making direct separation negatives onto panchro film. Or for making negative prints on RA-4... if you're into that sorta thing :wink:

    It's mainly just a thought experiment I guess.
     
  4. Photo Engineer

    Photo Engineer Subscriber

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    Chris;

    There is NO bleach before the E6 color developer. That is a BIG mistake.

    Second, the E6 color developer, intended to go to completion, is a fogging developer and cant work properly as a straight negative color developer. That is your second mistaken assumption.

    PE
     
  5. Athiril

    Athiril Subscriber

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    I've xpro'ed Reala using a first dev I made myself, and rest were E-6 steps, results were excellent. I would say many of them could even be projected, many of my C-41 positive xpro's appear colour balanced with a ~6500K backlight as opposed to 3200K. Ascorbic acid fiddles with the mask somehow - even after processing, I watched the mask change in colour before my eyes in an ascorbic acid solution.

    I've cross-processed Astia to a colour negative, using diafine as a first developer, then fix, bleach, colour developer, bleach, fix, stabiliser, with wash steps. The colour is exceptionally strong, I have one that has such strong colour on a portrait, that I can't completely colour balance it digitally, it is ridiculous.
     
    Last edited by a moderator: Apr 26, 2011
  6. holmburgers

    holmburgers Member

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    Forgive my ignorance of color processing steps! I'm looking at the big picture, and missing the details.

    So, I guess the color coupling fogging developer only works because the negative image is undevelopable at this point, ergo, basically it would fog the whole thing if there was no silver neg image. That certainly doesn't sound useful...

    Ok, well how about C-41 making a masked positive. This is probably the more intriguing route. What would a b&w reversal-type 1st dev do to a C-41 emulsion? Would it harm the couplers, the masking dyes, etc.? I guess the "bleaching" sequence would be tricky... how to remove the negative silver image? Hmm... I'm thinking myself into a corner...

    Now Athiril, I'm curious about your process for X-pro'ing Astia. Why did you have to have a 1st dev? I thought the color developer took care of both silver and dye.

    As is probably evident, I've never processed color and until now haven't tried to understand the processing sequences. However, a lightbulb was lit and I had to propose the idea.
     
  7. Photo Engineer

    Photo Engineer Subscriber

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    Well, Kodak actually made a masked color reversal film for duplicating purposes. It was not on the market very long due to low demand IIRC. C41 developed in E6 yields a low contrast positive image with an orange mask. Treatment in strong acid messes with the dyes and can remove parts of the orange color, but will also affect the other dyes as well also IIRC.

    PE
     
  8. holmburgers

    holmburgers Member

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    PE,

    I'm just going off the wikipedia entry for E-6, but I don't understand why the color developer in E6 is fogging if the reversal-bath/light-exposure achieves this. Nor do I understand how the existing negative image doesn't become more developed at this stage.

    As for removing the silver image in E6, it appears that this is achieved in a fundamentally different way than in b&w r.p. (a strong acid & dichromate), which would presumably harm the dyes..?

    Furthermore, why does E6 call for a pre-bleach and a bleach, followed by fixing. C-41 only requires a bleach and fix, and that takes care of both types of silver (halide/metallic), so I'm confused.. basically.

    These color systems are marvels of complexity!

    There's got to be a better way to cross-process film, by taking select steps from each process and combining them to make a unique process that is more suitable and less brute force.
     
  9. Photo Engineer

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    Chris;

    It would take pages to go into the theory behind these two processes, but here is the gist of things. NO developer develops all of the Silver regardless of time and temperature, unless drastic formulation changes are undertaken to do this. When you do, the developer will then fog the emulsion, and so these developers are generally reserved for color reversal. Second, the first developer must develop all of the silver as well, and therefore it is foggy by comparison to regular B&W developers. If the first developer does not develop all of the silver, the color developer will and thus you will have a high dye dmin.

    So, strong first developer to leave no Silver Halide in what will become the whites of the slide. Strong color developer to insure that every bit of Silver is developed.

    Since all Silver is developed and no Silver remains, the dye clouds are surrounded by 100% Silver metal which puts a load on the bleach by having to act on a lot of Silver, and also because the Silver may be surrounded by dye. So, the bleach is designed to act accordingly. Using Dichromate affects hardness, image quality and dye hue and stability. Dichromate bleaches are actually "Blixes" in the sense that they both bleach Silver and remove it at the same time. But, they are not good for color.

    A reversal color developer has about 2x the ingredients of a B&W or negative color developer.

    How is this?

    PE
     
  10. kevs

    kevs Member

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    Hi Holmburgers,

    How about trying Rollei CN 200 Digibase film? It's an unmasked C-41 film, so you could cross-process it without having the orange mask to deal with. I've never tried it myself, but there's a thread about it here. It might give you the results you are looking for.

    Cheers,
    kevs.
     
  11. holmburgers

    holmburgers Member

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    It's good, and I appreciate the description. Though I don't understand how "all" the silver can be developed in the 1st dev and yet leave a positive image of undeveloped silver that is necessary for the CC-developer to oxidize and create dyes. I guess by all you just mean most?

    What I'm attempting to say is this: how can we reversal process C-41 without resorting to simply putting it through the E6 process. Specifically, when in the process & how can we safely remove/desensitize the oxidizable media (negative silver image) before it is CC-developed?

    Does that make sense, or am I just whistling dixie?

    edit: Thanks Kevs. To be honest, I don't have a result in mind at the moment, and the idea of having a masked positive is actually a good thing in my eyes, since it helps with color reproduction. My thinking is that a reversal processed negative film with mask would be the finest scanning medium; having fine grain and color corrective masking. The orange mask could be compensated for "computationally" (that sounds better than digitally... hahah)
     
  12. Photo Engineer

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    Well, I should have been more specific.

    The first developer is designed to develop all of the silver that comprises the negative image (directly exposed Silver Halide) and the color developer is designed to develop all of the remaining Silver Halide.

    Yes, you can process C41 film in E6 to get a low contrast masked color transparency, but I doubt if any scanner is capable of handling it well. A scan of a color negative might be better. A masked slide would be hard to print as well being so low in contrast.

    PE
     
  13. holmburgers

    holmburgers Member

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    Well, just putting it through E6 is what I'm trying to change; doing that brings us right back to typical X-pro. It seems to me that using the appropriate color developer (CD-4) would yield better results, no?

    Hence, "cross-processing", but not really...
     
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  15. Photo Engineer

    Photo Engineer Subscriber

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    I am really not sure what you want to do.

    Sorry.

    PE
     
  16. holmburgers

    holmburgers Member

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    Here is my train of thought, if it's not clear...

    A C41 emulsion is designed to work with a developer containing CD-4, so it seems that putting it through a process that uses CD-3 is not ideal. I'm just trying to surmise if an alternative processing scheme utilizing a CD-4 developer as a 2nd developer can yield a positive in a way that is different from typical cross-processing, which is simply running a C41 film through the standard E6 process.

    If I'm embarking on a dead end path, just tell me... :wink:

    I guess what made me think of this was reading about making separation negatives. The integral masking in C41 films makes it so that no masking is necessary in the separation stage, whereas a slide, with it's admittedly imperfect dye set (for making separations), requires color-corrective masking in the separation stage. If I want to enlarge to a separation negative on panchromatic film, having a masked positive would be a boon, but the cross-processed results are of such questionable quality that this isn't a viable option.
     
  17. Photo Engineer

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    Yes, you can make an E6 color developer using CD-4. It will affect dye hue and image stability. The thing is, that the fundamental dye structures were intended for printing, not viewing and so at a later stage in the mechanical process, you would have to correct for this.

    PE
     
  18. holmburgers

    holmburgers Member

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    Hmmm... but I want to make a reversal process for C41 using CD-4, having nothing to do with E6. It sounds like you're referring to processing E6 in CD-4, no?

    If we develop C41 film in a contrasy b&w developer as a 1st dev, can we remove that negative silver image safely, and then utilize a CD-4 developer to bring out the remaining positive image?
     
  19. Photo Engineer

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    Ok, make a positive from C41 film using ANY process with ANY color developing agent will give a low contrast positive of some sort, but the dyes are not adjusted for the human eye, but rather for the use of a print material.

    Go here: http://www.kodak.com/global/en/professional/support/techPubs/e4051/e4051.pdf page 5 and look at the sensitivities and the dyes. Now go here: http://www.kodak.com/global/en/professional/support/techPubs/e4024/e4024.pdf and compare the same things. You will see a big difference in spectral sensitivity and in the hue of the dyes. These differences attempt to match the reversal film to the eye and the negative film to the print materials on the market. The print materials have dye sets that are more like the reversal film to remove any hue shifts or other color errors.

    PE
     
  20. holmburgers

    holmburgers Member

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    That is a very illustrative comparison and I see what you mean. It's interesting that the Portra curved doesn't show the individual dye curves, but it makes sense in light of what you're saying.

    I am not concerned with this theoretical C41-positive's visual appearance, but I am concerned with having "separable" layers. I'm looking at this from the perspective of scanning and/or making color separation negatives onto panchromatic film. In either instance, as long as the color channels are discrete enough that they can be separated from each other through the use of filters or computationally, its visual appearance is not important really.

    Issues with dye-stability and masking are what I'd like to preserve in a C41 positive.

    As usual Ron, thanks for taking the time to humor my queries.. :smile:
     
  21. Photo Engineer

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    Well, if you are scanning, you can fix color errors by digital masking.

    And, I am always glad to try and answer questions.

    PE
     
  22. holmburgers

    holmburgers Member

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    That's true, but for making analog separations it would be helpful, plus the finer "grain" of a reversal processed film is very appealing, assuming that wasn't outweighed by any other inadequacies.
     
  23. michaelbsc

    michaelbsc Member

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    Chris,

    Many things can be done computationally, but the concept of spectral separating the images onto pan film is intriguing, especially given the orange-mask.

    How would you accomplish this? Illuminate the image with a colored light source as we were talking about in thread a few weeks ago? Assuming you want RGB separations, then illuminate them with R, G and B light for the enlargements?

    If Ron's observations about the color balance being "not adjusted for the eyes" shift the required lighting, I wonder can those spectral shifts be accurately compensated using something like a diachronic enlarger head.

    Or maybe I misunderstand the problem totally.
     
  24. Photo Engineer

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    Michael;

    If I may answer, making separations onto B&W film from color negatives was one of the earliest Dye Transfer methods. The film used for the final image was Pan Matrix Film and the last supplies are in the hands of Ctein. You can go directly from the negative to the Matrix with full color and contrast correction.

    PE
     
  25. michaelbsc

    michaelbsc Member

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    Ok, then you are saying that I can shoot regular old C41, process it normally in C41 chemistry, then appropriately make separations onto pan film?
     
    Last edited by a moderator: Apr 28, 2011
  26. Photo Engineer

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    Yes. But without Pan Matrix, you cannot go further with Dye Transfer. You need another process.

    The filters used normalize the differences in the dyes and spectral sensitivities.

    PE