"Film-out" onto C-41 negatives - orange mask cancellation

Discussion in 'Misc. Hybrid Discussions' started by FilmCurlCom, Feb 13, 2018.

  1. FilmCurlCom

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    Hi!

    I read through many similar posts on the orange mask but did not really find an answer to my very specific question about the following experiment:
    I display inverted color images on my screen and re-photograph them with a carefully aligned camera on C-41 negative film.
    This gives me nice and sharp positives images like on slides but of course including the orange mask, which as explained is not like a filter, should correct certain colors, ...
    Would there be any way to have the source image's colors changed in such way beforehand that when re-photographing it, the changed colors and the mask's cancel each other out? If so, experimenting with different colors could show in which directions to go. Or is this something that can never work because it is simply not possible that way?

    Thanks!
     
  2. Rudeofus

    Rudeofus Subscriber

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    The magic property of orange mask is that it's always there: either (in case of no exposure) as visible orange mask, or (in case of exposure) as unwanted density. You get correct colors after inversion, because this constant density can be easily filtered away. BUT: you won't ever get neutral, transparent white with orange masked C-41 film.

    Would you settle with color plus lots (D > 1) of gray density? Such a thing would hardly be useful as slide ....
     
  3. OP
    OP
    FilmCurlCom

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    Hmm ok, so what you are saying is that I could get rid of the orange tint in my proposed way, but would end up with a kind of grayish overlay on top of my colors? And over exposing alot or other extreme measures will not change that ever?
     
  4. Arbitrarium

    Arbitrarium Member

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    ...why?
     
  5. OP
    OP
    FilmCurlCom

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    Why not? I said above it is for an experiment I am working on. When it works out fine I can show you why it's nice.
     
  6. calebarchie

    calebarchie Member

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  7. AgX

    AgX Member

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    The orange mask is basically a intentional, uniform, orange cast at the unexposed film that desintegrates during processing dependent on exposure.

    The idea behind the mask is to defy inherit deficencies in the image-forming dyes. As a result the colours of the negative, but especially the resulting positive, are more saturated, more truthful.
    The masking was invented in a time of true chemical photography with both a wet negative and positive, with both having those inherit deficencies.
     
  8. Sirius Glass

    Sirius Glass Subscriber

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    Again why? The orange mask is there so that the prints will have the best possible color match. Eliminating it will throw off the color balance and make proper color matching impossible.
     
  9. Rudeofus

    Rudeofus Subscriber

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    Let's assume for a second, you can expose a strip of C-41 color negative film with an arbitrary light source. The minimum density you can achieve is, if you look at the characteristic curve in Portra 400 data sheet, somewhere around (Dred = 0.2, Dgreen = 0.7, Dblue = 0.9). This is exactly the orange mask you see in unexposed and correctly developed Portra 400, and it's the absolutely brightest you can get. If you want this brightest color to have a neutral hue, you need to expose, such that Dred = Dgreen = Dblue = 0.9, i.e. a uniform gray strip with D = 0.9 will be the brightest neutral color you can create. With extra exposure you can then reach all colors in the range (Dred = 0.9, Dgreen = 0.9, Dblue = 0.9) + (ΔDred, ΔDgreen, ΔDblue) with ΔDred ≥ 0, ΔDgreen ≥ 0, ΔDblue ≥ 0.

    Enough math babble: the best you can get is something which looks like a color correct image on top of an ND 0.9 filter. This might be interesting from a theoretical standpoint, but not really useful for projection. The mightly 1000W lamp of my Goetschmann projector would be reduced to a measly 100W light bulb with such a slide.
     
  10. OP
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    FilmCurlCom

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    Thank you very much, now this is an answer that was very useful and interesting!!
    I don't understand all the "why" replies in here, they do not answer my original question at all and I already stated it is "an experiment".
    This in itself should be a good enough reason already, let's call it curiosity, wanting to know if I could cancel out the mask the same way one can cancel out noise with headphones that apply 180° inverted sound waves.
    So far experiments in that direction did not work at all, therefore my question to the experts here, if it was even possible at all, not to waste more film on that.
    Now I know more.
     
  11. MattKing

    MattKing Subscriber

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    Don't cancel out the mask - embrace it! It shows the way to colour purity.
    I guess this post belongs in the Ethics and Philosophy sub-forum.
     
  12. Prof_Pixel

    Prof_Pixel Member

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    That's sort of the reason for the orange color in the first place - it's there to correct for unwanted adsorption of the cyan and magenta image dyes. http://www.brianpritchard.com/why_colour_negative_is_orange.htm does a nice job of explaining this.
     
  13. AgX

    AgX Member

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    The idea behind the mask is, that after processing there again is a uniform orange cast (made up from the original cast meanwhile partially reduced and the new, bothering orange cast from the imaging dyes).
    Being uniform this final cast can easily be vanished by correcting filtration.

    This filtration is analogous to a 180° phase compensation the OP asks for.
     
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  15. tomfrh

    tomfrh Member

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    The colour absorption errors in each of the layers PLUS the mask equals a net orange cast which can easily be cancelled out with a complementary cast.

    You won't get a correct colour positive using orange mask C41 film
     
  16. Craig

    Craig Subscriber

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    You would if you used Vericolor Slide Film SO-279! That's what it was designed for, and has a built in blue mask to complement the orange. Of course, it's long discontinued.
     
  17. OP
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    FilmCurlCom

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    Thank you all for your replies!

    True, and you can actually still find that on Ebay.
    But PE himself once told me that with those films being expired for that long my chances for good results are slim.
    But who knows, maybe I will try that film eventually.
     
  18. tomfrh

    tomfrh Member

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    A built in blue mask! Far Out, Man!
     
  19. halfaman

    halfaman Member

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    There is also Rollei CN 200, it is an unmasked color negative film. Available in maco but only in 120 format.
     
  20. alanrockwood

    alanrockwood Member

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    I have been thinking about the orange mask lately, and I noticed something in the characteristic curves for C-41 negatives. It looks like the three curves are offset from each other in a vertical direction, and it also looks like the offsets are simple vertical offsets. Given that density is a logarithmic function, then if it is true that the characteristic curves are simply offset from each other in the vertical direction, then on the transmission scale it means that they are related to each other by a simple multiplicative factor. If so then it should be possible to compensate for the orange mask by simply illuminating the negative with a compensating filter, i.e. a light source whose spectrum compensates for the orange mask.

    A corollary to this is that if one simply multiplies each of the color channels in a scanned image by channel-dependent constants that should also simulate the effect of using a filtered illumination of the negative.

    On the other hand, if the vertical curves are not simply offset from each other by constant amounts then this scheme won't work.
     
  21. OP
    OP
    FilmCurlCom

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    Hehe, nope, I still have >10 of the 135 size CN200. They are incredible hard to find but I managed to get the very last ones a shop had after searching forever.
    I originally used CN200 for similar experiments but it is not a clear base film but has an aweful looking grayish base.
    So I stopped that and am using those films now as normal C-41 negatives whenever I am after a certain look (slightly muted colors, more grain, but still somewhat charming).
    You can see an example of it both here on my gallery as well as on my website.
     
  22. Rudeofus

    Rudeofus Subscriber

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    This is not an accident, but the main reason for using an orange mask: to create three independent characteristic curves in lock step with a constant offset. With all the other requirements imposed on film dyes (archival stability, high color saturation, ...) orange masked film seems to be the only technically feasible way to go.
     
  23. tomfrh

    tomfrh Member

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    That's the whole point.
     
  24. Sirius Glass

    Sirius Glass Subscriber

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    If color negative film could have been corrected without the orange mask, then the film would have been made without the orange mask. Kodak and the other companies did not add the orange mask based on the face that appeared on their morning toast, the orange mask is there because it is needed. If one wants to experiment removing it and printing as a learning experience that is all well and good, but do not think that you will ever be smarter than the photo engineers at Kodak, Fuji, Ansco, Agfa, ... et al and all the scientific research that they conducted.
     
  25. tomfrh

    tomfrh Member

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    Those people were amazing. I couldn't believe the complexity of the orange mask issues when I first read about it. The unwanted dye errors, the masking couplers, the resultant orange cast. It's sad that this technology has fallen away.
     
  26. Sirius Glass

    Sirius Glass Subscriber

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    It took me a long time to completely absorb the complexity and the necessity for each of the factors of the orange mask. There are many aspects that were juggled until a complete and robust solution was found.
     
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