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  1. #1

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    Medium format enlargements with 50mm instead of 75mm lens

    Yesterday i made some enlargements of medium format film with a 50mm lens instead of the correct 75mm lens. I did not notice any difference in my prints. My question is: is it really necessary to change lens when changing formats? I am using a durst AC707 autocolour enlarger with 645 negatives shot on a bronica. Both lenses are nikon.

  2. #2

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    I do believe that Nikon enlarging lenses are reputed to have a greater coverage than they are designed to be used with, which may be the answer. However I would contend that a Nikkor 80mm F5.6 gives better edge sharpness than the 50mm Nikkor if the prints were examined closely.

  3. #3

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    I do believe that Nikon enlarging lenses are reputed to have a greater coverage than they are designed to be used with, which may be the answer. However I would contend that a Nikkor 80mm F5.6 gives better edge sharpness than the 50mm Nikkor if the prints were examined closely. Especially if the enlargement were 12x9.5 or larger.

  4. #4
    MattKing's Avatar
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    If you have a 50mm lens on your enlarger that gives even, sharp coverage over your entire 645 negative, then it will work fine.

    In most cases though, a 50mm enlarging lens used for a 645 negative will result in lighter, unsharp corners in a print made from the full 645 negative.
    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

  5. #5
    ic-racer's Avatar
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    The coverage of all enlarging lenses is enhanced at low magnification. In fact when you get to the range of reductions, you can use a lens with a focal length equal to the diagonal of the print, even if the negative is much much larger.

  6. #6
    cliveh's Avatar
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    Use a 80mm.

    “The contemplation of things as they are, without error or confusion, without substitution or imposture, is in itself a nobler thing than a whole harvest of invention”

    Francis Bacon

  7. #7

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    I'd use the 75 or 80, if for no other reason than to preclude light fall-off from center to corner.

  8. #8
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    The sharp region is smaller than the lit region, so you will see corner softness earlier than you would with the correct lens. Consider the coverage to be a cone extending out of the lens - if the lens is further from the film (due to you making a small print) then clearly you can print a larger piece of film. This is why a too-short lens will work fine to print a 5x7 print but will fail horribly if you try to print a 16x20.

  9. #9
    RalphLambrecht's Avatar
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    the cone is a good metaphor.I may steel that one day if that's ok?
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  10. #10
    polyglot's Avatar
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    of course, but I'm sure there's a diagram to exactly that effect in your book...

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