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    More on ortho sensitive paper negatives

    The thumbnails below, with a new emulsion are intended to show an improved version of the spectral sensitivity and speed of paper negatives that I've been working with.

    The first thumbnail repeats the one from the previous post for reference purposes. The second is a better emulsion with a shorter green sensitizing dye than used in the first thumbnail. (The apparent red sensitivity is a harmonic of UV and so should be discounted, as there was no UV filter in the beam)

    The third thumbnail is the higher speed material exposed in-camera metered at ISO 200. In any event, sensitometric testing in-camera and on-easel indicate that this new emulsion is about 3 stops faster than the results from the last post. Optimizing it for fog and contrast are my next jobs. Tests to date indicate that at proper fog and contrast levels, this emulsion will yield a paper negative with a speed of about 80 - 100.

    When coated on film support, this emulsion loses about 3 stops due to the loss of back reflection and also due to chemical effects of being on a paper support vs film support. I have posted a discussion of these effects elsewhere. With proper chemical tweaking, I believe that this should only be a 1 stop speed loss.

    PE
    Attached Thumbnails Attached Thumbnails spectral sensitivity 1 AgBr and I reduced.jpg   ISO 200 wedge spectrogram.jpg   ISO 200 paper pos.jpg  



 

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