Color Theory Question

Discussion in 'Silver Gelatin Based Emulsion Making & Coating' started by Mustafa Umut Sarac, Aug 2, 2011.

  1. Mustafa Umut Sarac

    Mustafa Umut Sarac Member

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    If I have the RGB Curves for example of Kodachrome. How I can know how these RGB or CMYK curves works together. Is there a more detailed , 3D representation of it.
    Or a color mix function ?

    Thank you ,

    Umut
    Istanbul
     
  2. Bob Carnie

    Bob Carnie Subscriber

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    K is a black channel, you must mean cmy and rgb, I will ponder this question and may have to ask Dinesh my mentor this question.
     
  3. Mustafa Umut Sarac

    Mustafa Umut Sarac Member

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    Indian Guru Dinesh , Save my sprit :smile:
     
  4. domaz

    domaz Member

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  5. Monito

    Monito Member

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    Yes, it is colour mixing. Kodachrome is slide transparency film. So transmitted colours are mixed.

    In a colour monitor, Red, Green, and Blue light (relatively narrow bands of frequencies) are mixed to make colours, because transmitted colour is Additive. We perceive Yellow when Red and Green light are mixed. We also perceive Yellow when light in the yellow frequency range is radiated. This means that there are several combinations available to produce many colours. This is called "metamerism" and uses "metamers".

    In printed material, colour is reflected and so it is subtractive. Yellow is part of the CMY primary colours. It reflects yellow light. Just how that is constituted depends on the actual ink used.

    In a transparency film, colour is produced by filtration, so it is subtractive. The filter subtracts (blocks) light. White light has all frequencies (all colours). The white light of the light table or projector is filtered by the slide. Where the Yellow layer and the Magenta layer are both present (have Y and M tones in that area) they together filter out light to give the perception of Red.
     
  6. Leigh B

    Leigh B Member

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    Perhaps understanding the relationship between CMY (Cyan/Magenta/Yellow) and RGB (Red/Green/Blue) would help.

    White light is composed of Red, Green, and Blue light.

    If you remove the Red, you end up with Green + Blue which equals Cyan, so Cyan = minus Red
    If you remove the Green, you end up with Red + Blue which equals Magenta, so Magenta = minus Green
    If you remove the Blue, you end up with Red + Green which equals Yellow, so Yellow = minus Blue

    This is how filters work.

    If you look at a white light through a Magenta filter, you see Red plus Blue, which is called Magenta.
    If you then add a Cyan filter, so you're looking at the light through both filters one on top of the other, you only see Blue, because the Magenta subtracts the Green, and Cyan subtracts the Red.

    This is the way color slide films work. The filters in an enlarger color printing head work the same way.

    - Leigh

    BTW, the reason the Black (K) channel is added to form CMYK is that you can't get a clean black by combining the three subtractive primaries.
     
  7. Mustafa Umut Sarac

    Mustafa Umut Sarac Member

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    My question is totally different. For example , autochrome , there are 6 different colors at the filter. I ve posted the dyes. Dyes have a spectrum curve. And there is a published only RGB curve analysis of Autochrome.
    How can we calculate from these dye curves or RGB curves , how a RGB xyz color transforms at the film x2y2z2.
    And how can we see this transform at a graphic.

    Above posted software link , may be relates with this question but I dont know it solves the problem
     
  8. Julia

    Julia Member

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    Those are density curves, right? To interpret those in a regular colour space (say, Lab), you need to know the spectral properties of the dies.
     
  9. Leigh B

    Leigh B Member

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    Perhaps you meant 'dyes'. :D

    - Leigh
     
  10. Diapositivo

    Diapositivo Subscriber

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    Actually it must be "dies", is more "spectral" :wink:
     
  11. wildbillbugman

    wildbillbugman Member

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    Dyes can make you die, if you ain't carefull!
     
  12. DREW WILEY

    DREW WILEY Member

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    Color space can be based upon either a three-dimensional or four-dimensional axis model. There are probably a number of commercial services and software programs marketed for this purpose. The basic
    simplified ones which merely relate screen to printer output would be inadequate. Rather, someone would have to isolate every specific dye or pigment used in a particular medium and plot this with a continuous spectrophotometer, then map the gamut space. But I fail to see what value the result would be unless
    you have already studied color mapping and understand the implications. Breaking down the values for
    an obsolete color process would be quite difficult unless you have adequately sized samples of each
    primary component.