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  1. #11

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    Quote Originally Posted by Sanders McNew View Post
    ...My question: Does a graded paper change contrast depending on the light source?...
    First, realize that there will be differences between a grade 2 graded paper and a multicontrast paper printed through a grade 2 filter. See the discussion of that subject in the "Ilford Galerie vs. MG IV" thread:

    http://www.apug.org/forums/forum37/3...tigrade-v.html

    To simplify your question, let's list some assumptions.
    • We're comparing a graded paper with a multicontrast paper using a filter that results in a characteristic curve exactly the same as the graded paper. This won't happen in reality.
    • You'll print the same negative on both papers using the same pair of light sources, etc.

    In this hypothetical, the answer to your question is no. The graded paper does not change contrast; neither does the multicontrast paper. Both prints will, however, be subject to the Callier effect with a condenser source, resulting in elevated high print values. This physical phenomenon is a manifestation of collimated light bouncing around the actual silver clumps in a negative and is related to how closely spaced those clumps are. Since they are densely packed in the negative for high values in a scene, resulting values in the print become disproprtionately higher there. None of this applies to color negatives, where dye clouds rather than silver clumps exist, and no scattering is possible.

    The essential concept that may be difficult to get a feel for is that differences in light sources are an optical system characteristic independent of paper type. The only relationship between the two is that one must select graded paper grade or a multicontrast paper filter with appropriate contrast to match the negative and enlarging system. The different light sources don't know or care what paper one uses; they do what they do to project image scale regardless.

  2. #12

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    To really understand what is going on with cold light vs condensor (or even point source, a rare thing today), you have to read up some on what is called the Callier effect (no relation).
    In simple terms, as j-fr and Helen mentioned, highlights are affected the most. The quality of the light coming from a condensor is columnated, or linearized to pass through the emulsion. Scattering occurs when passing through the silver grains, which impedes the light's passage as it exits. This happens more in the highlights than shadows because of the greater density of silver. This increases the contrast in an artificial way, and an enlarged print will have more contrast than a contact from the same neg, since this doesn't happen in contact printing, and I believe it gets worse with greater enlargement.
    The Cold Light, on the other hand is already diffused, so this phenomenon doesn't occur as it passes through the emulsion, giving a better rendition of what is in the negative. The argument for using a cold light is that you can expand the contrast in film development, building better separation (and therefore information) into the final neg image.
    The first time I used a cold light (Aristo), I made a comparison with my condensor head, and found that I could use a higher contrast paper, giving me better shadow separation and detail, without "chalking" up the highlights. I never went back. Also, since I use 35mm, 2 1/4, and 4x5, I don't need all those condensors, you don't make any changes with a cold light when going from format to format.
    Google the term "Callier Effect" and you will find discussions on Photo.net.
    Someone chime in if I am off anywhere here.

  3. #13
    Matthew Gorringe's Avatar
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    Hi Sanders,
    I assume this is related to your question on getting more contrast out of grade3 Galerie?

    I wouldn't use a condensor system because the quality of the contrast changes and I happen to like a diffusion light source. In your case it's unlikely that you'll get significantly more contrast but the quality of that contrast will certainly change.

    Any chance you could hire a darkroom with a good quality point light source enlarger to try?

  4. #14
    Rolleiflexible's Avatar
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    Thanks, all. I appreciate the education. Sanders.

  5. #15

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    Evening,
    A little while ago there was an informative thread on the difference between diffusor and
    condensor in the forum darkroom->enlaring. Or maybe the little and hard to detect
    differences. I think it was at most just a few weeks ago it was active.

    -J

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