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  1. #21
    MattKing's Avatar
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    To add one stop neutral density, I put the extra 30 cyan of filtration in, because it just feels better to do so .

    It might be reasonable to assume, as well, that the magenta, cyan and yellow filters we are using would be similar in their imperfections, so using all three may be more consistent.

    Of course, my preference for all three may have something to do with the colour printing I used to do.

    Matt

  2. #22
    RalphLambrecht's Avatar
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    Quote Originally Posted by srs5694 View Post
    If the filters were theoretically perfect, the cyan filter wouldn't have any effect at all. RalphLambrecht is claiming that they have a significant effect, although he's not provided detailed data.
    Expose a sheet to a mid gray without any filter, then dial in some cyan, and print again. You'll find out how significant the effect of cyan filtration is. Filters have density. C60 has more density than C90. That's why the cyan filter isused by some as a neutral-density filter. No further data required!
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  3. #23
    RalphLambrecht's Avatar
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    Quote Originally Posted by Kirk Keyes View Post
    Right - it's all about how pure the cyan filter is in any particular enlarger. An ideal cyan filter will have no effect on typical B&W papers. A poorly made one may have a huge effect. Conversely, an enlarger with an ideal yellow and an ideal magenta filter will be all you need to get 1 stop of ND when using B&W paper that is insensitive to red light.
    Kirk

    What do you think should happen when I change the cyan filtration from C30 to C60? Nothing? Not so, the print gets lighter, because the filter is getting denser.

    It has nothing to do with pure, poor or ideal. A filter does exactly that, it filters. Color filters are bias and filter more of one wavelength than of another, but there is no miracle sharp cut-off, and there is no ideal cyan filter. A cyan filter filters all wavelengths of light, just a lot more red than any other wavelength. That's why all filters have filter factors. The denser the cyan filter gets, the lighter the print will get. To avoid that, apply the filter factor or make use of the effect, and use it as a neutral density filter. This doesn't mean it's a poor filter. It means, it's a filter.

    This is easy to test in 5 minutes in the darkroom.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  4. #24
    RalphLambrecht's Avatar
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    Quote Originally Posted by Kirk Keyes View Post
    Or, for B&W printing, you could just us 0/80/50 as the cyan filter will have little affect on a paper that has little red sensitivity.

    Printing on color reversal paper, it's just as you say.

    And, a photon is a photon, the Universe around. Some are visible, some are invisible, but they are all just photons. The speed of light is not in respect to the wavelength of the light, i.e. it's not only the speed of visible light, the speed of UV radiation, the speed of IR radiation, the speed of microwaves, the speed of x-rays. They are all photons, and all light, and it's simply the speed of light.

    I think Einstein would have differentiated this one if he had found it made a difference. He was a pretty smart guy, afterall...
    Kirk

    Please try that. C/M/Y 0/80/50 vs 30/80/50

    You will find that tey are different. The C30 component acts as a neutral density filter and lightens the print. A 60/80/50 filtration will be lighter yet, because there is even more neutral density filtration. They are not bad filters, they are just filters. That's how they work.

    A suggestion was made to dial in all three at once to get a neutral filtration as in C/M/Y 30/30/30. I agree with that. It works for color, because they cancel each other out. It works for B&W, because M and Y cancel each other out and cyan has a neutral effect anyway. If cyan has no effect, 0/30/30 should do the same as 30/30/30, and there should be no need for the cyan component. Of course, that is not so.

    If Einstein could have tested his theories in the darkroom; he would have done so. Some things are easier to try than to talk about.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  5. #25
    BetterSense's Avatar
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    To be picky, I believe the term 'visible light' is tautological. As I have been taught, 'light' is defined as the visible range of electromagnetic radiation (roughly the wavelength from 400-700 nm). Consequently, there is no such thing as ultraviolet or infrared light but only ultraviolet or infrared radiation. Light is visible by definition. Saying 'visible light' is like saying 'they arrived one after the other in succession'.
    I'm a materials scientist and I work with electrical engineers, chemists, and materials scientists on a daily basis, and I read and write technical research papers every day. Regardless of any dictionary definition, I can tell you that in the scientific community, the fact is that it is universally understood that "light" does not necessarily refer to visible light. In technical literature and in person, I hear the word "light" used to refer to radio waves, microwaves, infrared lasers, and xrays and gamma rays, blackbody radiation, and basically any electromagnetic radiation. I opine that the above quoted terminological opinion is quite incorrect and should be abandoned in the interest of understandability. There may be a lay usage of the word 'light' just as there is a lay usage of the word 'work' but in both cases I have to consider the respective definitions currently used uniformly by the scientific community as the ones to be touted about as "most correct".

    The quite distinct concept of 'visible light' is arrived at by integrating the luminance ("light") over one of various well-argued-over luminance functions that supposedly simulate the average human eye's sensitivity curve, to arrive at an artificial picture of "visible light". There is as parallel situation with sound. Scientists refer to everything from infrasonic waves in the earth's crust to far, far ultrasonic lattice vibrations in crystals as 'sound', quite apart from any individual's ability to hear it. If you hang around semiconductor scientists much, you will eventually hear of "phonons" which are quantum "particles" of sound which are shed to crystal lattices during energy transitions! I'm sure that won't fit in the groove of an LP.

  6. #26

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    Quote Originally Posted by RalphLambrecht View Post
    Expose a sheet to a mid gray without any filter, then dial in some cyan, and print again. You'll find out how significant the effect of cyan filtration is. Filters have density. C60 has more density than C90. That's why the cyan filter isused by some as a neutral-density filter. No further data required!
    As I've stated several times, I can't perform this test because my enlarger is a Philips Tri-Color unit with separate red, green, and blue channels; I have no cyan filter with which to test. Of course, I could go out and buy a whole new enlarger, or at least a cyan filter and enough other equipment to refit my current enlarger, but that's overkill to resolve a question that's unimportant to me personally.

    So basically, you're saying that cyan filtration has a significant effect on B&W exposure, but you've provided no details and you haven't even explicitly said that you've performed the experiment you recommend I perform. That leaves a big question in my mind about how significant the effect is. Does 100cc of cyan filtration reduce exposure by 1 stop? 1/3 stop? 1/10 stop? Less? It could also vary from one enlarger to another. Furthermore, there might be green/blue differences in a cyan filter, which could affect contrast -- perhaps not on all enlargers, but maybe in some. For these reasons, I stick to my recommendation to not rely on cyan filtration as neutral density for B&W printing, at least not without performing extensive testing to figure out what the enlarger and filter in question actually do.

  7. #27
    RalphLambrecht's Avatar
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    BetterSense

    In your opinion, should we use the term UV-light rather than UV radiation?
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  8. #28
    BetterSense's Avatar
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    I don't see how it matters. Neither is incorrect. Both could be confusing in the wrong context. The fact of the matter is people use both.

  9. #29
    RalphLambrecht's Avatar
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    Quote Originally Posted by srs5694 View Post
    As I've stated several times, I can't perform this test because my enlarger is a Philips Tri-Color unit with separate red, green, and blue channels; I have no cyan filter with which to test. Of course, I could go out and buy a whole new enlarger, or at least a cyan filter and enough other equipment to refit my current enlarger, but that's overkill to resolve a question that's unimportant to me personally.

    So basically, you're saying that cyan filtration has a significant effect on B&W exposure, but you've provided no details and you haven't even explicitly said that you've performed the experiment you recommend I perform. That leaves a big question in my mind about how significant the effect is. Does 100cc of cyan filtration reduce exposure by 1 stop? 1/3 stop? 1/10 stop? Less? It could also vary from one enlarger to another. Furthermore, there might be green/blue differences in a cyan filter, which could affect contrast -- perhaps not on all enlargers, but maybe in some. For these reasons, I stick to my recommendation to not rely on cyan filtration as neutral density for B&W printing, at least not without performing extensive testing to figure out what the enlarger and filter in question actually do.
    According to Lot-Oriel and Opto-Precision (the only manufacturers of Cyan filter, I know about), cyan-filter transmittance in the range of 400-550 nm is 80-90%, then quickly drops below 1%. This means that cyan filters filter up to 20% green and blue light in this range. This amounts to about 1/3 stop, which I call significant. Also, some papers are sensitive up to 660 nm (Forte to name one). A typical cyan filter filters will affect these papers.

    Again, 1/3 stop is significant to me, because I fine-tune my highlights to 1/12 stop, but I agree that a cyan filter is only of very limited use as a neutral-density filter.

    But since you continue to ask me to provide prove and detail, let me ask you a question. If you can't test for the effect of cyan filters,because you have no such enlarger, how did you prove to yourself that there is no effect? Why are you so certain? How did you verify your claim?
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  10. #30
    RalphLambrecht's Avatar
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    Quote Originally Posted by BetterSense View Post
    I don't see how it matters. Neither is incorrect. Both could be confusing in the wrong context. The fact of the matter is people use both.
    I agree, people use both, but common word usage and scientific correctness are not always the same thing. Maybe you're right, Oxford and Webster should change their definition of light and separate the term from sight to better reflect common usage. Until then, I'll stick to it, and as you said, That isn't wrong either.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

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