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Thread: Pre-exposure

  1. #1

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    Pre-exposure

    I have been pre-exposing my B&W negatives for quite some time for Zone II. Any members with experience on this technique who could contribute insight?
    Jack Rosa

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    Are you pre-exposing all of your negatives, or just the ones to be used in high SBR situations? I'm not too familiar with the reasons for pre-exposure. I always thought it was a tool to be used for high contrast subjects. How are you currently doing the pre-exposure?

  3. #3

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    Quote Originally Posted by JackRosa
    I have been pre-exposing my B&W negatives for quite some time for Zone II. Any members with experience on this technique who could contribute insight?
    I have used this technique because it has the opposite effect of preflashing the paper at the printing stage. In other words it compresses the shadows rather then compressing highlights.

    I have exposed extreme SBR scenes as high a Zone IV on the pre-exposure and then compensated my actual exposure by basing it on the highlight values.

  4. #4

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    Bleaching

    Jack-Alot easier to make up a dilute soluton of Ptt. Ferricyanide and PAINT away the black or lighten the highlites. Not all papers respond to this. Forte Poly V is the one I use and I learned the technique out of Bruce Barnbaums book.
    Regards Peter

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    Quote Originally Posted by peters
    Jack-Alot easier to make up a dilute soluton of Ptt. Ferricyanide and PAINT away the black or lighten the highlites. Not all papers respond to this. Forte Poly V is the one I use and I learned the technique out of Bruce Barnbaums book.
    Regards Peter
    Actually bleaching paper will increase print contrast...exactly opposite of what wants to accomplish when a negative of too great contrast exists. Preflashing paper will decrease print contrast by compressing highlights. Pre-exposing film will decrease contrast by compressing shadows.

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    To: Donald

    Compressing shadows? By pre-exposing, don't you move the low areas up in the curve, away from the toe? Wouldn't this actually increase separation in the shadows?
    Jack Rosa

  7. #7

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    Quote Originally Posted by JackRosa
    Compressing shadows? By pre-exposing,
    don't you move the low areas up in the curve, away from the
    toe? Wouldn't this actually increase separation in the
    shadows?
    I think an important point is being overlooked in this discussion.
    If one is seeking to move the low areas up the curve and thereby
    increase the separation, give the film an extra stop or two of
    exposure.

    A pre-exposure will do the same only at the toe. The scene be
    a very contrasty one, it will have the advantage. A Zone I
    pre-exposure I'd think always safe while a Zone II might
    be pushing it. I've the negative's density in mind.

    Also, I do not think has been mentioned the effective increase
    of the EI due to pre-exposure. Dan

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    Dan - excellent points, re: over-exposing and Zone I pre-exposure. Thanks.
    Jack Rosa

  9. #9

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    Quote Originally Posted by Donald Miller
    I have used this technique because it
    has the opposite effect of preflashing the paper at the
    printing stage. In other words it compresses the
    shadows rather then compressing highlights.
    Put the paper's and the film's toes, little exposed areas, on the
    left of the horizontal x axis of an xy graph. Put the density on the
    vertical y axis. Exposure increases towards the right along the
    x axis.

    Assuming both film and paper have very non-linear toe regions
    then the effect of pre-exposure should be similar. For both film and
    paper the for real exposure lies above the pre-exposure and the
    whole of exposure, hopefully, resides within the more linear
    portion of both curves.

    That's the way I see it. If I've overlooked some fact or reasoned
    wrong let me know. Dan

  10. #10

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    Quote Originally Posted by JackRosa
    Compressing shadows? By pre-exposing, don't you move the low areas up in the curve, away from the toe? Wouldn't this actually increase separation in the shadows?
    Nope what you are doing is adding a greater proportion of exposure to the lower zones then to the higher zones this will compress the low values. What you are addressing is increasing linear exposure. Pre exposure is non linear.

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