Advice on light-fall-off needed

Discussion in 'Darkroom Equipment' started by naaldvoerder, Aug 13, 2005.

  1. naaldvoerder

    naaldvoerder Member

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    Hi Forum,

    Until recently I was thinking of upgrading my EL-Nikkor 2.8 50 with a Apo-Rodagon. Yestrday however, I discovered that my enlarger shows some light fall-of towards the edges, wich can only be counteracted by stopping down. Will this diminnish the usebility of an Apo-Rodagon, which, if I understood correctly, could be used at a bigger aperture?

    Thanks for your comments.
     
  2. df cardwell

    df cardwell Subscriber

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    Which enlarger do you have ?
     
  3. resummerfield

    resummerfield Subscriber

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    Light falloff problems can usually be remedied. First, define the light falloff. With a 35mm carrier with a blank piece of film (clear, little density) in place and focused on the baseboard, expose a sheet of paper to a mid-gray. Then compare that to an exposure of a step tablet, to determine how much light falloff, in stops, occurs at various points on the paper. And do this a various apertures.

    I personally wouldn’t worry if the light falloff is less than ½ stop at 5.6. If more, you can probably modify the enlarger (clean the diffusion box, or condensers, etc). What type of enlarger are we talking about?

    Finally, the Nikkor 50/2.8 is a great lens. I would only consider an APO lens if I were doing critical color work.
     
  4. Paul Sorensen

    Paul Sorensen Member

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    I wonder if you don't have an issue with the upper bellows of your enlarger. (assuming it has one) Sometimes that will cause significant fall off with the Beseler condenser enlargers we use. Our solution is to put an empty carrier in the enlarger, focus using the edge of the carrier as your image, and adjust the bellows until the light is even across the frame.

    Paul.
     
  5. hortense

    hortense Member

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    Just try an edge burn of about 15% and see if that solves your problem. If that doesn't work do a + or - ...
     
  6. Donald Qualls

    Donald Qualls Member

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    If stopping down counters the light falloff, it's due to the lens, not the condeser/diffuser. That means the Apo-Rodagon may well fix it.
     
  7. dancqu

    dancqu Member

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    I was going to say the same. Dan
     
  8. df cardwell

    df cardwell Subscriber

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    Again, which enlarger do you have ? The problem could be caused by countless theoretical possibilities... but identifying the enlarger will make it an easy fix.

    Switching lenses is unlikely to solve anything.
     
  9. Claire Senft

    Claire Senft Member

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    A decent example of a 50mm El Nikkor N vs a 50mm Apo Rodagon N is going to be very little. Both lenses are highly suitable for b&w as well as color enlarging.
     
  10. naaldvoerder

    naaldvoerder Member

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    The enlarger is a German Dunco enlarger. It had a promissing reputation, but doesn't quite live up to it.

    Jaap Jan