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  1. #121

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    Quote Originally Posted by Nicholas Lindan View Post


    What I was proposing was something much simpler. Bleach the silver away from a uniformly stained pyro negative with no image (well the image of a blank wall or some such). Use the stained negative as an auxiliary contrast filter. See if this filter will alter the contrast obtained with say, #1, #3 1/2 and #5 filters.

    Although this sounds silly at first thought, it may give a negative result. This would be significant, the reasoning being:

    VC paper doesn't change highlight in contrast until one gets above #3 1/2 and so the stain may not have much effect of lowering highlight contrast at normal printing grades. The highlight contrast at normal grades is already at its lowest point and has no place lower to go.
    You are assuming that the optical properties are the same after bleaching. How are you validating this assumption?

    I did once an even more simple experiment: I put oxidized pyrogallol on a glass plate. Then I put the glass plate in the filter drawer of the enlarger. Oh yes it works. But what does it tell you?

    Jed

  2. #122
    Nicholas Lindan's Avatar
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    Quote Originally Posted by Jed Freudenthal View Post
    Oh yes it works. But what does it tell you?
    I have no idea. Why would I?

    How did it work? What did it tell you?
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  3. #123

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    Quote Originally Posted by Nicholas Lindan View Post
    I have no idea. Why would I?

    How did it work? What did it tell you?
    It was just filtering like yellow, and that was what I expected. It looks like a silly experiment, but I wanted to use as to calibrate the pyrogallol stain. I never finished this. It might bring more insight in the nature of the stain. But, the photographic results prevail.

    Jed

  4. #124
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    Quote Originally Posted by Jed Freudenthal View Post
    It was just filtering like yellow ... I never finished this.
    Then it is not really worth talking about anymore, is it?

    Quote Originally Posted by Jed Freudenthal View Post
    ...the photographic results prevail.
    What results? I'm under the impression you said the 'experiment' never went anywhere?
    Last edited by Nicholas Lindan; 03-15-2011 at 12:33 PM. Click to view previous post history.
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  5. #125

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    Quote Originally Posted by Nicholas Lindan View Post
    Then it is not really worth talking about anymore, is it?



    What results? I'm under the impression you said the 'experiment' never went anywhere?
    On the subject of these stains are so many publications, that I think, is there not anything that can be added. Of course much of this information is done with spectrophotometry and other analytical methods. But, what can one add to all that is known? Apparently, you want to use it with other analytical methods to investigate the properties of stain. But, it is up to you to solve that.
    Maybe you might get a proper insight in stain with simple procedures. But scientifically, this will not add much. I as a scientist, consider spectrophotometry a quite simple approach.

    Jed

  6. #126
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    Quote Originally Posted by Jed Freudenthal View Post
    On the subject of these stains are so many publications, that I think, is there not anything that can be added.
    I wasn't aware of this information.

    Would you be so kind as to post the journal references - I would like to read the articles.
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  7. #127
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    Quote Originally Posted by Jed Freudenthal View Post
    ... I put oxidized pyrogallol on a glass plate ... It was just filtering like yellow ...
    A question just hit - how did you prepare the oxidized pyrogallol?
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  8. #128

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    Quote Originally Posted by Nicholas Lindan View Post
    A question just hit - how did you prepare the oxidized pyrogallol?
    Pyrogallol in an alkaline environment and air will be oxidized.

    And, concerning the information on the stains you could start with:
    http://www.largeformatphotography.in...ad.php?t=22261

    As I remember, there are references in this discussion. And contact the people on details, because they made almost any measurement one can imagine, but with more or less sophisticated equipment. As I remember, the wavelength properties and densities of the different stains were investigated, and in one instance the reflection density of the print was measured.

    Jed

  9. #129
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    Quote Originally Posted by Jed Freudenthal View Post
    And, concerning the information on the stains you could start with:
    http://www.largeformatphotography.in...ad.php?t=22261
    I'd like to quote from that thread:

    We're all just weary of the constant bickering...

    Me too.
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  10. #130
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    Quote Originally Posted by Nicholas Lindan View Post
    I'd like to quote from that thread:

    We're all just weary of the constant bickering...

    Me too.
    Me too.

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