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  1. #1

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    What is the Watkins factor for phenidone?

    What is the Watkins factor for phenidone?

    thanks,

  2. #2
    MDR
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    Depends on the emulsion you're using. Or do you mean what the watkins factor is?

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    Quote Originally Posted by MDR View Post
    Depends on the emulsion you're using. Or do you mean what the watkins factor is?
    Let's start with that1
    Regards

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

  4. #4
    Snapshot's Avatar
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    If I recall correctly, the Watkins factor is the length time in which image highlights appears. This indicates the working speed of the film developer. A multiple of this time gives the total time in which an image will fully appear.
    "The secret to life is to keep your mind full and your bowels empty. Unfortunately, the converse is true for most people."

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    Wow, whenever you think you know most of the stuff ... there is something new to know.
    “Do your work, then step back. The only path to serenity.” - Lao Tzu

  6. #6

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    Quote Originally Posted by Snapshot View Post
    If I recall correctly, the Watkins factor is the length time in which image highlights appears. This indicates the working speed of the film develope. A multiple of the time give the total time in which an image will fully appear.
    Never heard of it, but if this is the case how can you have a "watkins factor" for a developing agent? It depends on the film, developer pH (and the rest of the developer formula), processing conditions (temperature, agitation) etc.

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    Maybe it is the "fudge factor" by another name?

    There seems to be a Derek Watkins, maybe he is related to this factor? http://opie.net/orphy/photo/dr/wkft-e6.html

    Another guess is that is a factorial calculation, based on the emergence time of the print/negative?
    “Do your work, then step back. The only path to serenity.” - Lao Tzu

  8. #8

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    It would have to be determined experimentally for each film and developer combination.

    http://www.earlyphotography.co.uk/site/entry_D89.html

  9. #9

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    Some values for film in various developers are given by L P Clerc "Photography",but not Phenidone.
    On p95-99 of "The Print" Adams notes "...watch closely as the print develops..locate..one..middle value area..and when that emerges (becomes faintly visible) note the time,...The total development time is the emergence time multiplied by this factor."
    By Adams method you have to find the factor yourself.
    R. Henry says Alfred Watkins originally used it in 1893 for negatives but it works equally well for prints.

  10. #10

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    When used alone phenidone produces a VERY low contrast image. In order for it to be used in a practical developer it must be combined with some other developing agent like hydroquinone or ascorbate. I have never seen a Watkins factor listed for phenidone used alone and it would really not be very useful for the reason stated.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

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