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  1. #11
    Photo Engineer's Avatar
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    Most simply put, the nucleating agent inhibits the surface negative image and internal image as well, but where there is no exposure, it allows the internal fog to develop as if it were image. Thus, no negative image forms and only a positive "fog" image forms.

    PE

  2. #12
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    Here are two threads over on F295 about my experience with using this Efke direct positive paper.

    Overall I find it needs significant preflash, more than I normally give paper negatives, to get anywhere near normal contrast, even when rating the EI at less than 1.

    ~Joe

  3. #13
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    Joe;

    I would imagine that this type of paper would suffer from a huge reciprocity effect. With a pinhole camera, you might be seeing that due to the long exposures. IDK for sure though. Any thoughts?

    PE

  4. #14
    Joe VanCleave's Avatar
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    PE:

    You're probably correct about the huge reciprocity effect, but this link refers to me using an exposure of ~1.5 - 2 seconds at F/16 in an improvised refractive lens, LF box camera, for the several self-portraits posted. I'm not sure if 1-2 seconds implies significant reciprocity or not.

    I'm also curious about using elevated developer temperatures with this paper; tests I did this week of Arista's grade 2 RC (conventional) paper, used as an in-camera negative in both glass and pinhole lensed cameras, indicates I can get nearly EI=25 by using Ilford's Universal paper developer, diluted 1+15, at 80f. That post can be found here.

    None of my tests are textbook scientific in accuracy, however; they merely represent the degree of accuracy I can get using my normal processing method.

    ~Joe

    PS: My avatar is from one of the Efke direct positive self-portraits.

  5. #15
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    I would tend to think that 1 - 2 seconds would be too short for a huge amount of reciprocity to take place, even in this type of paper. I do know that these emulsions can be made to yield a variety of contrast ranges depending on sensization and silver levels.

    I did notice your avatar. If I had one, it would be yellow with a red "K" on it.

    PE

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