Additive colour printing, understanding lamphouse?

Discussion in 'Color: Film, Paper, and Chemistry' started by Ted Baker, Nov 5, 2018.

  1. Ted Baker

    Ted Baker Member
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    I am doing some research to assist in a project I am working on.

    I am reasonable competent in using what is to me a standard colour enlarger for RA-4 materials. i.e. something like this.

    upload_2018-11-5_12-9-20.jpeg

    I would like to understand some parts of descriptions in this Kodak Document regarding making BW negatives from colour negatives.

    The document is here: https://www.kodak.com/uploadedfiles...ost_Production/Archival_Films/2238_TI2404.pdf

    I understand most of it, pretty well. However my knowledge is sketchy when Kodak, refers to additive and subtractive lamphouses. I realize these are being used in motion picture context of course.

    Am I correct in assuming that when Kodak refers to subtractive printing, they are referring to what I am used to. i.e. single mixed lightsource, that is then filtered.

    And for Additive printing, they are referring to lamphouse with separate lightsources that can filtered or given individual times times?

    Like this

    [​IMG]
     
  2. Martin Rickards

    Martin Rickards Member
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    Look up the Philips colour enlarger for additive
     
  3. AgX

    AgX Member

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    Don't let you get confused. Take the advice under "subtractive lighting". This will be a "white" light from a naked enlarger bulb. Depending whether you got a plain or halogen lamp its colour temperature will be different anyway. And you might have to adjust.

    (Yes, with additive printing you would have three lightsources of red, green and blue, and by one way or another to make them into white light in effect.)
     
    Last edited: Nov 5, 2018
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    Ted Baker

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    Thanks, I think I am getting it. I am interested in both methods for research purposes. With the additive method, I assume you have three narrow spectrum sources, of RGB, which is perhaps why the filter recommendation is different. e.g. for the additive case they don't even recommend a green filter, as they assume the spectrum is already sufficiently narrow. (maybe)
     
  5. AgX

    AgX Member

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    But adding a filter nonetheless would not harm.
     
  6. Martin Rickards

    Martin Rickards Member
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    I think you use all the light sources simultaneously but adjusting the length of time for the RGB exposures.
     
  7. ic-racer

    ic-racer Member

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    I have a Philips additive. As you mentioned, the three colored lights can be varied in intensity. The other interesting thing about this enlarger is that it is a condenser. Not many color-head condenser enlargers out there. I use it for B&W printing, using the Blue and Green lights for exposure and adding the Red light for white-light focusing. BTW the popular Ilford 500 multigrade head is also a similar additive head with Blue and Green lamps.

    [​IMG]
     
    Last edited: Nov 5, 2018
  8. AgX

    AgX Member

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    Yes, a condensor enlarger, but not a point-source one, more like those with an opalescent bulb.
     
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    Ted Baker

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    Any ideas why the only recommend 2B when using an additive light source?

    PE, referred to something in thread sometime earlier but I have not figure it out.
     
  10. Lachlan Young

    Lachlan Young Member
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    It cuts UV at 395nm - the 70, 98, 99 setup is what seems to be regarded as the most accurate separation filtration set - dig around in the Wratten number resources & you should get the transmission ranges & cut-offs.
     
  11. georgegrosu

    georgegrosu Member
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    I do not understand well what you want to do with KODAK Panchromatic Separation Film 2238.
    In cinematography, is used to make three black-white interpozitives after a color negative, and after to obtain the color interngative.
    Black-and-white interpozitives are color selection (separation) copies made for long-term archiving from originals color negative.
    The three black-white interpozitives are made instead of the color interpozitive.
    In the first phase, the negative color image is copied by an indigo, green and red filter on the black-and-white pancromatic film.
    Three black-and-white interpozitives are obtained.
    Each black-white interpozitives is a black-white extraction for a fundamental area of the spectrum.
    These three black-and-white interpozitives are then copied, in the second phase, in turn, through the same indigo, green, red, red filters on a color film,
    after which the color interpozitives are processed.
    In order to obtain the final color interngative, six rows of copying with the recommended filters are required.
    Exposure of black and white interpozitives can be make on the Kodak Eastman Panchromatic Separation Film type 5235 film that has a high latitude,
    fine grain size and high resolution.
    The development of black and white interpozitives is make in the negative developer D 96 at a contrast factor of 1.0.
    There is a possibility that by altering the contrast factor of the black-and-white interpozitives, the color balance of interngative will improve after the contrast
    of the original color negative.
    In order to execute the interngative color, in the second phase, we can use the Eastman color intermediate film that develops in the ECN 2 process at the contrast factor 1.0.

    PS Both the additive system and the substractive system use a single bulb.
    On the additive system (see Bell & Howell Model C- http://www.brianpritchard.com/Model C.htm ),
    the light from the bulb is divided into three beams of dichroic mirrors.
    At the end, the three light beams are summed up in one light.
    About the filters here:
    https://www.kodak.com/motion/Produc...odak_Filters/WRATTEN_2_Filters/default.htm#s3
    The additive system uses filters: blue, green and red.
    The substractive system uses filters: yellow, magenta and cyan.

    George
     

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  12. Bill Burk

    Bill Burk Subscriber
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    Wow look at that beautiful printer! It has filter slots right past the light valves. That's probably where the 2B (or 2E for duplicate negative) goes for the Blue valve and the 70 for the Red valve. Maybe the Green dichroic's are "good enough" without a filter?

    It sounds like either way you are making three separate exposures to a set, one that's just blue light, one that's just red light and one that's just green light.

    If you have one of those beautiful printers, then the 70 and 2B or 2E filter is all you need, you're good to go.

    But the typical colorhead is not mentioned in the Kodak document for this kind of separation printing. I don't think you are going to get the colors you will need with Yellow Magenta and Cyan.

    So you're either using this RGB printer with the red and UV filters or you're using a white light source and the red green blue and UV Wratten filters.
     
    Last edited: Nov 6, 2018
  13. georgegrosu

    georgegrosu Member
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    I hope you do not laugh at me.
    By 1975 I bought my first Meopta Opemus Standard.
    To be able to make color pictures I needed the filters.
    In Romania, in those days, they were not found filters on the market.
    I had a friend electromechanical engineer who had the passion of stereo photos.
    He had made a stereo camera from two Smena 8 cameras.
    I developed the color negatives and made her positive color print for he.
    He felt compelled to me and did not know how to reward me.
    He first made a color filter drawer adapted for Opemus.
    Then I got some old filters I, V, R that he adapted for the Opemus.
    When some negative colors did not give good photos with the Janpol Color
    lens, I used the triple exposure option using the three color filters.
    I hope this can help someone with an idea.

    George
     

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    Ted Baker

    Ted Baker Member
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    that provides a clue, so I am guessing that the BW separation film is more sensitive to UV light than the print and inter negative/positive films that the light source is normally designed for?

    i.e. the blue and green from an additive lamphouse are sufficiently narrow for the green to not need any further filtration and only blue needs a little tweak at the lower end of the spectrum.

    Thanks George, I am doing research, so I don't know exactly want I want to do until I understand things a little better. My research regards blasphemous and unmentionable stuff:wink:

    But this thread has confirmed a few things, I am still curious about the need for the 2B or 2E with the additive process. I understand why the need for the 70.
     
  16. georgegrosu

    georgegrosu Member
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    To make black-and-white interpozitives on KODAK Panchromatic Separation Film 2238 you need the film, the recommended filters and the concrete possibility of copying the three interpozitives exactly in the same place for make the color internegative !!!!

    Ted Baker “My research regards blasphemous and unmentionable stuff.”
    In such things I really do not know.

    George
     

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  17. Martin Rickards

    Martin Rickards Member
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    Didn't that Polish Janpol lens incorporate colour filters? I've never seen one and maybe it wasn't that model.
     
  18. AgX

    AgX Member

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    Last edited: Nov 6, 2018
  19. georgegrosu

    georgegrosu Member
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    This is the lens Janpol Color https://images.search.yahoo.com/yhs...-ddc-linuxmint&hspart=ddc&hsimp=yhs-linuxmint
    He was very comfortable working with him when I was making color photos on paper.
    The combination of substractive filters (yellow, purple or azure) on make by simply moving the two buttons on the side.
    In substractive calibration one or two filters are used to correct the color dominance.
    If the three filters (yellow, purple and azure) are used, then the gray color also appears.
    From here comes the name of the substratum.
    I mean, if you put three filters in front of a light bulb (yellow, purple and azure that give a gray) then the light will be weaker - it drops.
    With the additive, when mixing three colored lights (blue, green and red), the white light will emerge - that is, it gathers.

    George
     
  20. AgX

    AgX Member

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    The designations "subtractive" and "additive" were not chosen by accident...
     
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    Ted Baker

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    That part I get, I guessed as much, I still would like to understand why a 2B or 2E is recommended for the blue exposure with an additive lamphouse, while a 89 is required for the subtractive lamphouse.
     
  22. georgegrosu

    georgegrosu Member
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    AgX said:
    The designations "subtractive" and "additive" were not chosen by accident...
    That part I get, I guessed as much, I still would like to understand why a 2B or 2E is recommended for the blue exposure with an additive lamphouse, while a 89 is required for the subtractive lamphouse.

    I apologize for bothering you with my English.
    I allow myself to answer the above question addressed to AgX.
    Considering that the optical system of the substractive printers differs from the additive printer, and the exposure light to be identical on both additive and substrates printers,
    the recommended filters (2B and 2E .....) are used.
    You can trust Kodak.

    George
     

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  23. OP
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    Ted Baker

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    Yours posts and others were very helpfull.

    I think I have figured why 2B and 2E are used with the additive lamphouse.
     
  24. Bill Burk

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    Blue 98 right?

    I see you are getting close, but have this to add, maybe it will help.

    I bet you could use a 47B and 2B to make interpositive on this film with a subtractive lamphouse. The 98 gives same filtration with one filter (I guess that makes it a better choice for that step - fewer surfaces to keep clean).
    You need to use 47B and 2E to make dupe neg on this film because there isn't a composite equivalent.

    PE could explain why you need to take away a little more violet when making dupe neg, I am sure it's all about color balance.

    So you don't need a blue or green filter with the additive system (though you have to put UV over blue), guess it's all done with mirrors.

    You got me to wonder why you need a deep cut red filter on the additive system. That made me wonder about the "purity" of the red dichroic mirror which led me to this page that shows the shape of (what I guess is a standard) red mirror's filtration

    https://www.uqgoptics.com/materials_filters_colourBeamsplitter_red.aspx

    I'm thinking the red dichroic is too pure, and the film was designed for the deep cut so it needs the matched red filter
     
  25. AgX

    AgX Member

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    Basically additive and subtractive filtering are equal in effeciency, but your experience showed that there may be exceptions with the spectral characteristics of the filters in use.
    George, maybe you could go in detail, why in your case the subtractive filtering failedd, but the additive worked.


    Technically speaking, at least when automatisation is involved, the substractive system has its drawback. As there has to be some mechanism to control filters. Whereas in an additive system a mere timer is sufficient, making it much more apt for automatisation.

    However this involves a time-lag: either there are three complete seperate exposures, as in working with one light source, or there are three light sources working, starting at same time, but ending a different times.
    This makes burning and dodging either difficult or impossible.

    Philips' additive system does not work by time, but by light intensity, thus all three exposures are truly simultaneously.
    Making it usable like a subtractive system.
     
  26. Arklatexian

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    I am going to jump in here and ask if Kodak Panchromatic Separation Film 2238 was also the film used (3 films) in a "one shot" color camera where the final print was a dye transfer? Also was this not also the way Technicolor was shot (three B&W films being exposed simultaneously in one camera and then printed via the dye transfer process onto one film from which copies were made?) I jumped in over my head but I always thought the subject was interesting. I have some dye transfer prints made 60 years ago by a lab from 4x5 color transparencies that I sent them. They made the separation negatives and kept them for about 6 months in case I wanted reprints. Closest thing yet to archival color prints from film......Regards!
     
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