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  1. #21

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    Quote Originally Posted by MDR View Post
    Why would it be easier more steps are necessary to make a copy negative than a direct enlargment. Also looking at the Pentacon example which was designed for chloride emulsions that were only sensitized for UV-light the exposure times using a 50w mercury vapour lamp as lightsource were not that long.
    Because the two processes mentioned in the OP are so very slow and by slow we are talking about exposure times for cyanotype prints of from several minutes to several hours. Trying to get that much UV light thru the small aperture of an enlarging lens would take a very long time. This is also in addition to the fact that most glass formulations do not pass much UV light. UV spectrophotometers use cuvettes (special liquid containers) made of fused silica instead of glass. Remember too that UV light degrades most plastics including those used for film base. So one needs to limit the exposure time. If a copy negative is lost it is only an inconvenience not the loss of a precious image.

    Any silver halide emulsion is orders of magnitude faster than the two processes mentioned. BTW emulsions do not have to be sensitized to UV light which is in their normal sensitivity.
    Last edited by Gerald C Koch; 01-10-2014 at 09:16 PM. Click to view previous post history.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  2. #22
    MattKing's Avatar
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    Todd Gangler moved into his carbon printing work as a result of working with the Fresson lab on an early project.
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  3. #23
    Bob Carnie's Avatar
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    learn something every day thanks

    Quote Originally Posted by Hexavalent View Post
    AFAIK = As Far As I Know

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