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  1. #21
    holmburgers's Avatar
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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.
    If you are the big tree, we are the small axe

  2. #22
    michaelbsc's Avatar
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    Quote Originally Posted by holmburgers View Post
    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.
    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.
    Michael Batchelor
    Industrial Informatics, Inc.
    www.industrialinformatics.com

    The camera catches light. The photographer catches life.

  3. #23
    Photo Engineer's Avatar
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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

  4. #24
    michaelbsc's Avatar
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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 michaelbsc; 04-28-2011 at 09:17 PM. Click to view previous post history.
    Michael Batchelor
    Industrial Informatics, Inc.
    www.industrialinformatics.com

    The camera catches light. The photographer catches life.

  5. #25
    Photo Engineer's Avatar
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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

  6. #26
    michaelbsc's Avatar
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    Quote Originally Posted by Photo Engineer
    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
    Shouldn't I be able to duplicate those filters, or make changes to accomodate another pan film's different response, using a diachronic source?
    Michael Batchelor
    Industrial Informatics, Inc.
    www.industrialinformatics.com

    The camera catches light. The photographer catches life.

  7. #27
    Photo Engineer's Avatar
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    Yes, you can, but what can you do to make a print is another matter.

    The filters are WR98, 99, and 70 and the exposures and contrast are adjusted to give a neutral in the process you are using.

    PE

  8. #28
    holmburgers's Avatar
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    Michael, I know exactly what you mean. I wondered the same thing for a long time, whether the orange mask would make separations difficult. But along with what Ron is saying, it's not a problem.. something I was quite surprised by!

    I actually have in front of me a copy of Wall & Jordan's 'Photographic Facts & Formulas' from the library, and it explains this very well.

    Basically, the orange mask is a product of two separate masks. In the two layers that require masking (cyan & magenta), the couplers are made to be colored themselves. Upon processing, the colored-couplers are destroyed where the image density is, and left to remain where there is none. Thus, the coloring matter is inversely related to the dye image.

    Cyan has unwanted blue & green absorption, so the coupler in this layer is reddish and acts to mask these unwanted absorptions. The magenta layer has unwanted blue density, and the mask here is made to be yellow.

    Interestingly, as is the case in all printing schemes as far as I know, yellow is good enough to not require masking. Damn that yellow...

    Now if that wasn't enough, the dye-transfer printing matrices must also be masked to account for unwanted absorptions in these dyes. So first you have to get good clean information from your separations, and then you have to "unmuddy" the waters again during printing.
    If you are the big tree, we are the small axe

  9. #29
    michaelbsc's Avatar
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    Ok, it sounds like despite the fact that we have a significant hurdle in finding the "proper" filter settings using a fair amount of empirical testing, in theory there is no reason we couldn't eventually work out the details to shoot C41 and print separations optically.

    Mountainous, but possible.
    Michael Batchelor
    Industrial Informatics, Inc.
    www.industrialinformatics.com

    The camera catches light. The photographer catches life.

  10. #30
    Photo Engineer's Avatar
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    The Kodak Dye Transfer book (reproduced here somewhere in a PDF) and Jim Browning's web site explain all of this in detail.

    BTW, a masked color negative film has a positive mask image that contains the correction information.

    PE

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