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Thread: Any density plots for pyrocat-HD on VC paper?

  1. #1

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    Any density plots for pyrocat-HD on VC paper?

    I would like to get some data on the effect of the stain in pyrocat-HD negatives when printed on VC paper. Has anyone plotted a density curve which they could share?

    I would normally do this myself, but I move house a lot and don't expect to have the printing stuff out of storage for 6 months or more. I will be shooting "uncalibrated" until then, so want to see if pyrocat will do what I want or if I should go down the compensating developer path.

    Thank you!

  2. #2
    Kirk Gittings's Avatar
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    Re: Any density plots for pyrocat-HD on VC paper?

    for a REALLY compensating developer try divided Pyrocat HD http://www.pyrocat-hd.com/html/TwoBathPyrocat.html
    Thanks,
    Kirk

    at age 70:
    "The woods are lovely, dark and deep,
    But I have promises to keep,
    And miles to go before I sleep,
    And miles to go before I sleep"

  3. #3
    Drew Wiley
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    Re: Any density plots for pyrocat-HD on VC paper?

    Pyro plots can be misleading due to the stain, and different brands of VC paper have quite different characteristics in this respect. There are a lot of pertinent variables the plots simply won't tell you. In the real world, it's easy to get a good marriage of the two. But you'd have to be a lot more specific about film, paper, paper developer, style of VC printing, etc.

  4. #4

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    Re: Any density plots for pyrocat-HD on VC paper?

    Drew,

    As I am looking for plots, I am willing to accept what someone may have. If they list what film, paper etc. they at least I have a starting point to estimate how much the compensation effect will be in my application. Ideally someone will have done a full process calibration so: Exposed film X with a step wedge, developed in pyrocat-HD, printed on paper Y using filtration which would normally give grade Z, developed paper... then produced a reflection density plot of the step wedge. But I will take any measurements that someone can share.

  5. #5
    Drew Wiley
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    Re: Any density plots for pyrocat-HD on VC paper?

    A lot depends on how the specific image stain respectively affects each emulsion layer, and this differs paper to paper. But at least you've specified your exact
    developer, since different flavors of pyro have different types of stain. Sandy King might be your best resource on this one, since it's his baby to begin with.

  6. #6

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    Re: Any density plots for pyrocat-HD on VC paper?

    I know this information is out there already. Try http://unblinkingeye.com/Articles/PCat/pcat.html for example.

  7. #7
    ic-racer's Avatar
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    Re: Any density plots for pyrocat-HD on VC paper?

    Quote Originally Posted by rurmonas View Post
    I Has anyone plotted a density curve which they could share? !
    Yes, many times, and in all cases the results are not different than that obtained from a slightly different combination of filters. I'd just ignore the stain effect and move on.

  8. #8

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    Re: Any density plots for pyrocat-HD on VC paper?

    ic-racer

    So I am not understanding something here. There are numerous references on the internet to the compensating effect of the stain. Even Sandy King has commented on this effect. I can only think that the type of VC paper you are using is not greatly affected by the stain colour which develops on the film you are using. Could you mention which film and paper you are using?

  9. #9

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    Re: Any density plots for pyrocat-HD on VC paper?

    The effect of the stain from pyrocatechin and pyrogallol negatives on VC printing seems to be a bit of an urban myth in the photo world, one that I believed in as well until and exchange with Nicholas Linden, who has done extensive research on the effects of the stain on the response of VC paper, convinced me otherwise.

    In a nutshell, and as ic-racer maintains, the stain has no appreciable effect on the filtration of VC papers. It, alone, is basically a grade 2 filter and, when using other filtration, simply adds neutral density to the overall filtration, but does not effectively change contrast for any particular area of the negative, either low or high density.

    I believe Mr Linden (of Darkroom Automation) has, out of frustration, given up on explaining this again and again to people, but you may find some of his earlier posts intresting. I would search here and on the APUG site.

    Best,

    Doremus

  10. #10

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    Re: Any density plots for pyrocat-HD on VC paper?

    Quote Originally Posted by Drew Wiley View Post
    A lot depends on how the specific image stain respectively affects each emulsion layer, and this differs paper to paper. But at least you've specified your exact
    developer, since different flavors of pyro have different types of stain. Sandy King might be your best resource on this one, since it's his baby to begin with.
    I quit printing with VC silver papers many years ago and don't have any paper plot densities for Pyrocat-HD on these type papers. Making density plot is complicated by the fact that VC silver papers have several different green and blue sensitivities in the emulsion, and by the fact that the amount of stain is proportional to silver density, so high density negatives have a higher percentage of stain density than silver, and vice versa.

    In general the impact of pyro stain on VC papers is similar to that of a #1.5 - #2.5 VC filter. Stain adds printing density, but how much varies with the DR of the negative, the spectral absorption of the paper, and the spectral power distribution of the printing light. In printing with VC papers contrast is controlled by the amount of green light relative to the amount of blue light that makes up the total exposure, so in essence you have a process with a variable exposure scale, and to plot you have to fix that scale with a certain filter or mix of green and blue light. Once you have done that making a density plot is similar to making plots for any other process.

    Sandy
    http://www.sandykingphotography.com/
    For discussion and information about carbon transfer please visit the carbon group at groups.io
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