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  1. #41

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    Quote Originally Posted by JPD View Post
    So one can say that a yellow-green shade is just that, and is not a mix of anything?
    Indeed.
    There is a band of wavelengths we call "green". And there is a (more narrow) band of wavelengths we call "yellow". (And other parts of the spectrum we need not concern ourselves with now).
    And there is a transition area which we would call neither "green" nor "yellow". Or both, depending on our mood and what we ate yesterday.
    That area is not a mix of "green" and "yellow". Just different wavelengths, different colours we do not have a proper name for.

  2. #42
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    Quote Originally Posted by Q.G. View Post
    Green never contains yellow.

    The impression of green you get when mixing blue and yellow paints is because green light is not absorbed by those paints.
    It's green, because it does not contain yellow (and blue, etc.) anymore.
    Yes, there is a whole book out on watercolor and mixing of colors that's titled Blue and Yellow Don't Make Green where the author (a guy named Wilcox IIRC) explains that phenomenon.

  3. #43
    JPD
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    Quote Originally Posted by Q.G. View Post
    Indeed.
    There is a band of wavelengths we call "green". And there is a (more narrow) band of wavelengths we call "yellow". (And other parts of the spectrum we need not concern ourselves with now).
    And there is a transition area which we would call neither "green" nor "yellow". Or both, depending on our mood and what we ate yesterday.
    That area is not a mix of "green" and "yellow". Just different wavelengths, different colours we do not have a proper name for.
    That makes sense. I'm going to use this knowledge on my friends, attack them like a Besserwisser Bf 109.
    J. Patric Dahlén

  4. #44
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    Quote Originally Posted by JPD View Post
    So one can say that a yellow-green shade is just that, and is not a mix of anything?
    Yellow-green shade can be a single, monochromatic spectral spike between green and yellow wavelengths (what you describe), or it can be a mix of pure green and pure yellow wavelenghts, or it can be a mix of pure green and pure red wavelengths, the red one being much lower in level, or pure green and orange, or it can be a continuous region from green to yellow, or from green to red, lowering in level towards red, etc. etc. etc. If you give up a little in saturation (which is hard to evaluate, after all), you may even have a mixture of bluish-green and pure red, and that mixture still looks like yellow-green!

    So again, there are countless possibilities and our eyes cannot make difference. Some of them may be rendered differently by different color films or different digital cameras, but mostly they try to mimic the eye vision as much as possible.

    Our eyes only detect three broad overlapping wavelength regions. So, monochromatic, pure yellow gives equal signal to both "red" and "green" detectors because the spectral sensitivities of "red" and "green" detectors in our eyes overlap. If they didn't overlap, we would see monochromatic "in-between" colors black which wouldn't be very nice. And, for example, a signal of 80% "green" 20% "red" would translate as "yellow-green shade" in our brain.

    The only thing we can judge by our eyes to some extent, is that when we see VERY pure and saturated RED, GREEN or BLUE, then we can know they are relatively narrow spikes relatively near to specific wavelengths, and there are "not very much" other wavelengths present. But recognizing these very pure and saturated colors is not that trivial, and this works only for just those three colors.

  5. #45
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    Explanation in detail

    Here is the complete explanation in figures of additive, subtractive and pigment colors. Make your own decision about yellow! And magenta for that matter!

    PE
    Attached Thumbnails Attached Thumbnails color - spectrum and filters.jpg   color - additive.jpg   color - subtractive.jpg  

  6. #46

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    Good attachment. Forget the pigment mixing part though. The theory can't really be put into practice. That's why nobody actually paints using primaries

    Sorry I know that was way off topic...

  7. #47

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    The Sounds of Slience cannot be heard by the Deaf...

    I have a migraine headache comming on so excuse please my ill thought out mumblings!

    The above observations by HRST are rather profound...
    it is good to contemplate that outside of the human mind, there are no colors... only wavelengths, and things that absorb/reflect wavelengths.
    Color is everybit as synthetic as is pleasure, pain, thought and conciousness.
    It is our way of being able to interact with the world around us.
    We colorize the world so we can make sense of it.

    Well, maybe my migraine has me... by the eyeballs!
    Last edited by Ray Rogers; 02-02-2011 at 03:31 PM. Click to view previous post history.

  8. #48
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    The material above has nothing to do with film. It is as the eye would see it. Nothing is misleading. If you imply that the prism generated spectrum is wrong, then please explain. If you believe that the additive or subtractive color demos are wrong or misleading, please explain for all of us. This material comes from the Kodak Manual "Color as Seen and Photographed".

    Explain please, how it is misleading!

    PE

  9. #49
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    You have not explained, in any way, how the 3 demo photos above are misleading, or how my statement urging others to make their decision is misleading! You just bring in information about photons and energy levels. I was trying to simplify things for the readers and you are trying to kick it up a notch!

    PE

  10. #50
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    Quote Originally Posted by Q.G. View Post
    I have.

    But will again, in a way you perhaps better understand?


    We are talking about emulsions and their spectral sensitivity.
    Are emulsions not spectrally sensitized by dyes? If so, colour addition and subtraction are relevant.
    - Ian



 

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