Using larger condenser for smaller negatives

Discussion in 'Enlarging' started by agenkin, Jan 30, 2008.

  1. agenkin

    agenkin Member

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    There are three available condensers for my enlarger (Durst M700) - Unicon 50, Unicon 85, and Unicon 105. I understand that the number part (50, 85, 105) corresponds to the diagonal length of the negative that can be printed with this condenser, so the 50 is for the 35mm, the 85 is for 6x6, and 105 is for 6x9.

    What are the drawbacks of using a larger condenser (say, the 105) for printing smaller negative sizes? Should the lens be chosen depending on the negative size, or on the condenser size?

    In other words, can I use the 105 condenser to print 6x6 negatives with an 80mm enlarging lens?

    Many thanks for any input!
     
  2. Konical

    Konical Subscriber

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    Good Evening Arcady,

    I haven't used a Durst, but I assume that most condenser enlargers have similar characteristics. Most likely, using the larger condenser for a small negative will just mean somewhat less light concentration and, perhaps, a slightly longer print exposure. I don't think you'll see much difference, if any when you compare prints using the "right" and "wrong" condensers. That's the case with my Beseler 45 anyway.

    Konical
     
  3. richard ide

    richard ide Member

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    Arcady
    The condenser focal length is matched to the lens focal length. If you use a larger condenser, I think you are restricted to a longer focal length enlarging lens to get the desired illumination of the negative. The light source image is focused inside the enlarger lens. Very critical for point source illumination but you might be able to get away with it with a diffuse source.

    Regards
     
  4. Ronald Moravec

    Ronald Moravec Member

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    Using a condenser too large will very slightly darken the corners. If you match say a 100mm lens with 6x7 condensers and print a 35mm neg, then illumination will be uniform, however the available print size will be very small compared to a 50mm lens which will get darkened corners.
     
  5. 23mjm

    23mjm Member

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    I have a Beseler 67 enlarger and and own both the 35mm and 6X7 condenser. The only difference is the 35mm condenser focuses the light so it prints the 35mm twice as fast as when I use the 6X7 condenser ( or one stop faster, if you will) I have gotten lazy and left the 6X7 condenser in and the prints are the same, I just double the time.
     
  6. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    On my Omega D-II there was originally only one condenser set for all formats, and it works, though now I usually use a cold light head instead. They later added 35mm and 6x9 condenser sets, which should increase light output for those formats, but larger condensers should produce even illumination on smaller formats in general.
     
  7. agenkin

    agenkin Member

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    Thanks for the replies, everyone, although they are a bit in conflict with each other.

    What Richard writes makes sense (about condenser matched to a lens focal length), I wonder why the theory doesn't meet the practice for those who reported using larger condensers with shorter lenses.

    Is there a good book or an online resource explaining in detail how a condenser enlarger works?
     
  8. richard ide

    richard ide Member

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    I have tried to find detailed information in the past and so far have not found any information as detailed as I would like. To paraphrase an entry in the SPSE Handbook: The design of a condenser system may be easier to accomplish by test setups on an optical bench than to design one on paper first. There are very short articles in many photographic books, but not much regarding things like design. Ihave the head of an industrial camera projector where all elements of the system were designed around the lens used. This functions far better than anything else that I have used.
     
  9. Ole

    Ole Moderator Staff Member Moderator

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    The purpose of the condenser is to focus the light at the entrance aperture of the enlarging lens, so that all the available light is used in the printing.

    That's why I have a crate full of condensers for my Durst 138S - different lenses need different condensers to give even and focussed illumination.
     
  10. 23mjm

    23mjm Member

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    The condenser on my Beseler enlarger does not focus the light. What it does is provide a flat smooth light across the negitive. The bottom of the condenser is a flat milky white piece of plastic, but it is a color head, it that matters.
     
  11. agenkin

    agenkin Member

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    So, it's not a condenser, then, I think, but a diffuser.
     
  12. dancqu

    dancqu Member

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    Doubly diffuse + a condensed light source. I've considered that,
    a bottom diffuser disk, thin and placed within the condenser
    housing at the condenser's bottom. Was that a DIY, the
    bottom piece of plastic? Dan
     
  13. Tony Egan

    Tony Egan Subscriber

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    The short answer to your question is yes you can do what you suggest in your OP. At the cheaper end of the market there are condenser enlargers with one condenser for formats from 35mm to 6x7 e.g. the Meopta Opemus 7 I use sometimes. Provided you match the lens to the negative format - 80mm for 6x6 - then I doubt you could spot any difference with the naked eye. As someone suggested there may be slightly less light fall off using a condenser intended for a slightly larger format and bigger minimum lens aperture but again I would suggest practically immaterial to your final print.
     
  14. dancqu

    dancqu Member

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    I wondered about that reasoning myself upon receiving
    the instructions for my Omega B8 from Classic Enlargers.
    The instructions left one with the impression that
    a shorter focal length enlarging lens REQUIRED
    some one of two supplementary condensers.

    Mr. Knoppow may have negative format and light
    levels upon the easel in mind. Small formats generally
    require greater magnification so a more intense level
    of light upon the negative in order to print with
    reasonably short exposures.

    As has been mentioned a single set of condensers
    which provides illumination of the largest format
    will do for any smaller format though the level
    of illumination at the negative stage will be
    that of the largest format.

    Supplementary condensers for smaller formats are
    an EXTRA and not supplied with all enlargers. Dan