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Thread: Paper Negative Reversal Process (In camera positives)

  1. #21

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    Re: Paper Negative Reversal Process (In camera positives)

    Quote Originally Posted by sapata View Post
    From n. 7, everything is made in normal light condition, correct?
    I guess you can make step 3) and beyond with lights open. For BW film reversal I do that.

  2. #22
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    Re: Paper Negative Reversal Process (In camera positives)

    I though I might have a go with potassium metabisulfite (which is the chemical I have) and didn't work. Everything turned black...I'll post the results when I buy the right chemicals
    Mauricio Sapata
    www.mauriciosapata.com

  3. #23

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    Re: Paper Negative Reversal Process (In camera positives)

    I have tested some variables:
    No rinse
    Second light exposure step
    Pre flash

    No rinse: possible but shortens chemicals usability
    Second exposure: from step 5
    Pre-flash: helps with darker tones

    I don't know about weaker second developer. The image gets more difficult to develop and black to appear.
    Cheers
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  4. #24

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    Re: Paper Negative Reversal Process (In camera positives)

    Quote Originally Posted by gtmatias View Post
    I have tested some variables:
    No rinse
    Second light exposure step
    Pre flash

    No rinse: possible but shortens chemicals usability
    Second exposure: from step 5
    Pre-flash: helps with darker tones

    I don't know about weaker second developer. The image gets more difficult to develop and black to appear.
    Cheers
    Click image for larger version. 

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    You should not avoid rinse... it's the single not harmful step.

    First: do process lights open after rinsing out completely first developer, in this way you will see well what happens and if something fails.

    >>> Check bleach bath works ok. Bleaching has to clear all black areas that 1st developer turned black, if after bleach you have black in the paper then bleaching was not good, mix fresh bleach or use another bleach.

    You can develop a strip of paper with open lights to obtain a black thing, then rinse and bleach it, to see if bleach clear all black and converts it to a pure white strip.


    >>> Paper has emulsion on it, the share of emulsion that has not been exposed&developed in the 1st development will turn black in the second development, if your result is too black then you can expose more or develop more in the first development (or less in the second). The more black you have after 1st development the less black you will have after the second development. 1st Development time may control contrast, so you have to balance exposure vs development time to control both average density and contrast. But use also a grade of paper to adjust contrast, if too much contrast use grade Soft (1)

    >>> as a secondary control factor you may shorten the second development, to not develop all emulsion left by the bleach process. As you have lights opens you can decide when the paper is dark enough.

    >>> With preflash, also make a "contol strip", don't make a preflash for all the sheet, but by moving the dark slide at 2cm intervals you get the effect for different preflash intensities.

    You have to do 3 additional things: calibrate, calibrate and calibrate.

    Get Beyond The Zone System book ($4) and learn how to calibrate film. From the spot metering in each scene spot and exposure you may predict what density (grey level) you will obtain in the paper.

    If you use a sheet holder you can "slide inside" the dark slide at regular intervals, blocking light in an area on the paper to have different exposure times on the paper, so you have a test strip.

    Let me encourage to insist in this, it would be rewarding when you obtain nice results with that, it's a unique process sporting an scarce resource: authenticity !

    Please share your images !


    PD: you can make the exposure "bracketing" with strips vertical in the sheet and the flash bracketing in the other sense, so you'll have a matrix of squares, you should shot a uniform scene with remarkable texture.

    From a single shot you may find a good starting point.
    Last edited by Pere Casals; 17-Jan-2019 at 04:52.

  5. #25
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    Re: Paper Negative Reversal Process (In camera positives)

    Nice one... I'll get the chemicals needed. Thanks!
    Mauricio Sapata
    www.mauriciosapata.com

  6. #26

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    Re: Paper Negative Reversal Process (In camera positives)

    Peres Casal,

    i've been testing using your formula to:
    . better understand where things may get wrong
    . get better control on contrast
    . Get out some variables as "visual inspection"

    As a secondary objective I would like to experiment using it as "à lá minute" system. So, I asked myself what would happen if I didn't rinse (avoiding steps and getting everything more portable to a small darkbox).
    It shorely works. It has some problems:
    more prone to contamination.
    the chemicals get exhausted more quickly.

    Either way, I would like to use, at least the rinse after first developing and after clearing bath.

    Could a stop bath be used as rinse after first developer? What do you think?


    I had some trouble with first developer some time ago:
    When it was expired the image got really dark and some wave pattern appeard.
    If it doesn't develop completelly, the image got much dark.

    When I get some time, I'll use it again.

  7. #27

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    Re: Paper Negative Reversal Process (In camera positives)

    Quote Originally Posted by gtmatias View Post
    So, I asked myself what would happen if I didn't rinse (avoiding steps and getting everything more portable to a small darkbox).
    Nothing wrong to experiment, but if a rinse is in a processing then we should ask why it is specified before bypassing it. One thing it can happen is toxic gass generation from mixed chem, so we should have some care with that.




    Quote Originally Posted by gtmatias View Post
    Could a stop bath be used as rinse after first developer? What do you think?

    Yes, of course. See Darkroom Cookbook, Chapter 9:

    While a running water bath will not stop development as rapidly as an acid stop bath, it
    will slow it down to the point that the amount of residual development is insignificant. This
    is because, depending on its strength, it takes an acid stop bath approximately 15 seconds to
    halt development and a running water bath takes approximately 30 seconds. The difference
    in the negative image could not be measured. If you are still not convinced consider that the
    slight additional development will automatically be factored in when you run your film development
    test.


    So the single difference is that water stop bath takes 15 seconds more to stop development completely, this can be compensated by shortening development time by 5 or 6 seconds, perhaps.

    If you agitate a bit in the water then it will stop as fast than with the acid stop bath, because pH goes neutral faster.

    Acidic stop bath can be harmful in a number of ways: Fumes (if acetic concentrate) are not good for people, it can generate bubbles inside emulsion, and not all fixers are acidic, transporting acid to an alkaline fixer has no sense.

    Nothing wrong if using an acidic stop bath, but a water bath is as good as the acidic one. If a chem manufacturer wants an acidic stop bath then he says it in the datasheet, for example Adox CMS 20 (with Adotech II) case says "After the development you MUST use an acidic stop bath before fixing. Do NOT use plain water.", see datasheet. But this is a very specific case.

    In the other side C-41 and E-6 chem does not use an acidic stop bath after first developer, that is a BW developer. So...

    Me, I use plain water except for CMS 20.

  8. #28

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    Re: Paper Negative Reversal Process (In camera positives)

    Toxic gases? Maybe.
    The Chemicals may interact in other ways. Who knows!

    Anyway, this process must always made in a well ventilated space (metabisulphite has a quite harsh gas)

  9. #29

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    Re: Paper Negative Reversal Process (In camera positives)

    Quote Originally Posted by gtmatias View Post
    Toxic gases
    http://www-ehs.ucsd.edu/lab/pdf/phot...ing_mccann.pdf
    If you search "gas" in that pdf you have a dozen of situations.

    just we have to be careful with some chem...

    I use dichromate for reversal, this one has to be handled with care.
    Last edited by Pere Casals; 17-Jan-2019 at 15:20.

  10. #30

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    Re: Paper Negative Reversal Process (In camera positives)

    Sorry I haven't checked in, in years. I'm coming back. Real soon. Have lots I want to play with. At any rate, I did document my experimentation on Flickr. For those of you wanting to see the progression that I had started with to the end that you seen as the original post, here's it is.

    I believe throughout I have been shooting it at ISO 3. Colour tinting I have found is caused entirely from first development.

    The thread is here: https://www.flickr.com/groups/101104...7642870149194/

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