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  1. #1
    DrPhil's Avatar
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    UV vs visible in non-pyro negatives

    Over the past month I have developed over 150 negatives in pyrocat. One thing that I have noticed from reading about pyro is that many use it for alt processes. As I understand it, the stain responds differently to UV wavelengths over the visible (mostly blue) wavelengths used in enlarging. Apparently many people use pyrocat negs for dual purpose silver and platinum/palladium. My question is how do non-pyro negatives work with alt processes? For example, will a D76 1:1 negative respond to UV and Blue wavelengths equally?
    Facts are facts; however, perception is reality.

  2. #2
    clay's Avatar
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    Quote Originally Posted by DrPhil
    My question is how do non-pyro negatives work with alt processes? For example, will a D76 1:1 negative respond to UV and Blue wavelengths equally?
    D-76 1:1 negs will work fine if processed to the appropriate density range. I have many nice palladium prints from D-76 developed negatives. Because they have a density range of 1.8-1.9, they would be impossible to print in silver. My UV densitometer gives the same visual wavelength density range as the UV wavelength density range for D-76 negs. Stained negatives, on the other hand, read VERY differently on the visual channel than the UV channel. My nice stained negatives with a UV density range of 1.9 only have a visual wavelength density range of around 1.3, which is very printable on grade 2 or grade 1-1/2 paper.

    So the answer to question 1 is : They will work fine if processed appropriately and the answer to question 2 is: yes, D-76 negs respond to UV and Blue equally, unlike stained pyro negs.

  3. #3

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    Quote Originally Posted by DrPhil
    Over the past month I have developed over 150 negatives in pyrocat. One thing that I have noticed from reading about pyro is that many use it for alt processes. As I understand it, the stain responds differently to UV wavelengths over the visible (mostly blue) wavelengths used in enlarging. Apparently many people use pyrocat negs for dual purpose silver and platinum/palladium. My question is how do non-pyro negatives work with alt processes? For example, will a D76 1:1 negative respond to UV and Blue wavelengths equally?
    Most alternative processes need a light source high in UV light, although many of them also have some sensitivity to light in the near UV, violet an blue. The stain of Pyro negatives functions as a very strong actinic filter to UV light and increase the effective printing contrast. Negatives developed in non-staining developers such as D76, HC110, etc. pass UV and Blue light about equally well.

    The dual-purpose is possible with stained negatives because the effective printing density is much greater for UV processes than for Blue sensitive processes. For example, a typical FP4+ negative developed in Pyrocat-HD for about seven minutes will have an effective printing density range of about 1.05 for Blue light but around 1.35 for UV light. You could print this negative on a grade #2 silver paper and also with a standard 25/75 mix of pt./pd. with just a small amount of contrast control.

    Sandy
    Last edited by sanking; 08-29-2004 at 12:25 PM. Click to view previous post history.

  4. #4
    gainer's Avatar
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    First, pyro by itself usually refers to pyrogallol. Pyrocat HD uses pyrocatechin, AKA catechol or pyrocatechol. The stains are of different color. Both stain images are more dense to UV light than to visible. One of the advantages quoted for pyrogallol, specifically PMK, is that it can be used equally well on VC and alternative process. The alternative processes generally require a higher contrast negative because they are printing-out contact processes that are self masking. The yellow stain image adds much more to the contrast under blue or UV light than it does to visible or blue-green light. The differential may be in the other direction when comparing pyro prints on graded paper with alternative processes.

    Pyrocat may not be as much different. You will have to ask Sandy King.
    Gadget Gainer

  5. #5
    gainer's Avatar
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    I see that while I was mulling over what to say, Sandy said most of it and some I didn't say.
    Gadget Gainer

  6. #6

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    Quote Originally Posted by gainer
    One of the advantages quoted for pyrogallol, specifically PMK, is that it can be used equally well on VC and alternative process. The alternative processes generally require a higher contrast negative because they are printing-out contact processes that are self masking. The yellow stain image adds much more to the contrast under blue or UV light than it does to visible or blue-green light. The differential may be in the other direction when comparing pyro prints on graded paper with alternative processes.

    Pyrocat may not be as much different. You will have to ask Sandy King.
    The brown stain of Pyrocat-HD is a more effective filter for UV light than the yellow/green stain of the pyrogallol based PMK and Rollo Pyro. There is consequently a larger difference between Blue printing density and UV printing density with Pyrocat-HD than with these developers, and when the goal is a dual purpose negative the larger the difference the better.


    Sandy
    Last edited by sanking; 08-29-2004 at 12:58 PM. Click to view previous post history.

  7. #7

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    Sandy wrote, "The brown stain of Pyrocat-HD is a more effective filter for UV light than the yellow/green stain of the pyrogallol based PMK and Rollo Pyro."

    I suspect you will think I'm nit-picking, and I understand English is often not a very precise language, but I would like to point out that the "brown" color of a PyroCat HD neg and the "yelow-green" color of a PMK or Rollo neg do not predict negative absorbances in the UV. There's nothing intrinsically special about one stain appearing brown or yellow-green when considering UV.

    One cannot make assumptions on the absorbance of a material in UV simple by looking at the color of that material in any visible wavelength. I think we all saw that demstonstrated with Sandy's comparison of UV measurements of his Kodak and Stouffer step wedges. Sandy said all of his tablets looked pretty neutral in visible light, but his Stouffer tablets transmitted more in UV than the Kodak one. Who would have guessed this by looking at them?

    So what I'm trying to point out here is that your sentence would be more accurate by saying, "The stain of Pyrocat-HD is a more effective filter for UV light than the stain of the pyrogallol based PMK and Rollo Pyro." Or pehaps, "The stain of Pyrocat-HD, which happens to appear brown, is a more effective filter for UV light than the stain of the pyrogallol based PMK and Rollo Pyro, which happens to appear yellow-green."

    Nit-picky, perhaps, but it is an important principle to remember none-the-less.

    Kirk

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    Quote Originally Posted by Kirk Keyes

    I suspect you will think I'm nit-picking, and I understand English is often not a very precise language, but I would like to point out that the "brown" color of a PyroCat HD neg and the "yelow-green" color of a PMK or Rollo neg do not predict negative absorbances in the UV. There's nothing intrinsically special about one stain appearing brown or yellow-green when considering UV.

    Kirk
    I disagree with you on this one Kirk. From color theory one would expect a "green" or yellow/green filter to transmit more blue light spectra than a yellow or brown filter as such it is not far fetched that it would block more UV as well. Visual observation should give us a strong indication of the "probable" behavior of the stain. Of course this would then have to be verified with the appropriate measurements.

    As to the behavior of non staining developers, Clay had it right, pyrocat, pyro etc have the "ability" to be used for both silver and alt processes. OTOH my recent test of TMX400 with HC110 show similar results to Clay's. UV absorbtion is proportional to the amount of density or perhaps I should say silver halide content.

  9. #9

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    Quote Originally Posted by Kirk Keyes
    Sandy wrote, "The brown stain of Pyrocat-HD is a more effective filter for UV light than the yellow/green stain of the pyrogallol based PMK and Rollo Pyro."

    I suspect you will think I'm nit-picking, and I understand English is often not a very precise language, but I would like to point out that the "brown" color of a PyroCat HD neg and the "yelow-green" color of a PMK or Rollo neg do not predict negative absorbances in the UV. There's nothing intrinsically special about one stain appearing brown or yellow-green when considering UV.

    One cannot make assumptions on the absorbance of a material in UV simple by looking at the color of that material in any visible wavelength. I think we all saw that demstonstrated with Sandy's comparison of UV measurements of his Kodak and Stouffer step wedges. Sandy said all of his tablets looked pretty neutral in visible light, but his Stouffer tablets transmitted more in UV than the Kodak one. Who would have guessed this by looking at them?

    So what I'm trying to point out here is that your sentence would be more accurate by saying, "The stain of Pyrocat-HD is a more effective filter for UV light than the stain of the pyrogallol based PMK and Rollo Pyro." Or pehaps, "The stain of Pyrocat-HD, which happens to appear brown, is a more effective filter for UV light than the stain of the pyrogallol based PMK and Rollo Pyro, which happens to appear yellow-green."

    Nit-picky, perhaps, but it is an important principle to remember none-the-less.

    Kirk
    Picky, Picky, Picky!!!!

    I understand the point that you are making in regard to the proper expression of what Sandy was saying. But Christ do you iron your shorts too?

  10. #10
    DrPhil's Avatar
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    Gee whiz,

    All I wanted to know was if a guy with a non-UV capable densitometer wanted to print on Pt/Pd could he use his blue wavelength measurements for determining proper development. This was all assuming the use of a non staining developer of course.

    Clay seems to have answered this question for me.

    The idea of using pyrocat HD to create dual purpose negatives is appealing. However, I also want to be able to measure what I am working with.
    Facts are facts; however, perception is reality.

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