How to reduce output from cold light enlarger?

Discussion in 'Enlarging' started by jon koss, Sep 8, 2004.

  1. jon koss

    jon koss Subscriber

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    I recently ran out of graded fiber base paper and ended up reaching for a box of graded RC. I am actually quite pleased with the prints and will continue to use the paper. The enlarger is an Omega 4x5 with the Omega cold light.

    Here's the rub: The paper is way too fast for my setup. If I print at my sharpest f/stop then my times are uncontrollably short. To get times I can live with I must stop all the way down. I can literally watch the grain blur as I stop down, so I know I am giving up sharpness/acutance.

    Has anyone come up against this? Are there neutral density filters for the Omega? I would prefer not to peck around with electrical mods because I do not want to zap myself and I do not wish to possibly spoil a lovely setup.

    Any help is welcome.


    jon
     
  2. Donald Miller

    Donald Miller Member

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    I would consider adding neutral density into the light path above the negative by adding equal amounts of color printing filters(C,M,Y), if you have them. If you don't then I would look to material like Rosco Lux which comes in neutral shades of gray of varying densities.
     
  3. jnanian

    jnanian Advertiser Advertiser

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    aristo also sells a dimmer that can reduce your output.
     
  4. Ed Sukach

    Ed Sukach Member

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    What lens/es are you using? I have two Rodagons on my Omega and they are both front threaded for 40.5 mm filters. Certainly, the usual Neutral Density filters may be used ... from 2x to 10x.
     
  5. gainer

    gainer Subscriber

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    I don't know much about cold light enlargers, but would expect them to have a filter drawer far enough above the neg carrier to be out of focus on the base board. If that is the case, you might try using a piece of black window screen in the filter drawer.
     
  6. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    Cold light heads usually don't have a filter drawer, because they need to be close to the neg for even light distribution, but it's possible to put gel filters between the head and the neg, and I've seen an arrangement where someone made a filter drawer that only added 1 inch between the head and the neg with no ill effects. I'd go with the suggestion of adding an ND lighting gel between the head and the neg or an ND filter to the lens with a step-up ring if you don't happen to have the right filter diameter. I suppose you could even add a yellow filter, which you probably have on hand, below the lens, since there is no variable contrast issue and graded papers are mostly blue sensitive.
     
  7. sparx

    sparx Member

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    Perhaps i'm being thick here but i was always led to believe that smaller aperture = sharper image, both in picture taking and printing. Is this not the case?
     
  8. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member Moderator

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    A smaller aperture increases DOF and reduces certain aberrations, but increases diffraction, so the optimum aperture is not typically the smallest one.
     
  9. Jim Chinn

    Jim Chinn Member

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    I don't know about your head exactly, but my older D2 with an Aristo cold light uses a white plexiglass diffuser to even out the illumination. If you have something similar, you could take that peice to a plastics retailer and they could cut an extra one to put on top or a thicker one that should reduce light output.
     
  10. juan

    juan Subscriber

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    I had a glass place cut a round piece of ground glass (they probably called it dusted or some such thing) the diameter of the cold light. I dropped it into the enlarger where the cold light fits in, then added the cold light on top. It added even more diffusion and cut the light by a couple of stops or so.
    juan
     
  11. jnanian

    jnanian Advertiser Advertiser

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  12. paul ron

    paul ron Member

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    Don't you have an under the lens filter arm?... put your ND filter there or just tape it on for now. Otherwise get another plastic difuser which will cut your light by another 2 stops.
     
  13. jon koss

    jon koss Subscriber

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    Thanks jnanian for the link. When I saw your first post I assumed you were suggesting an electrical kluge of some kind. But the dimmer in the link looks like it was made for my unit. Is the standard Omega cold light indeed an Aristo unit?

    Jon
     
  14. wfwhitaker

    wfwhitaker Member

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    Jon,

    Do you have the "Omegalite" or do you have one of the cold lights which have been made (Aristo, Zone VI, etc.) to fit the Omega?

    -Will
     
  15. jon koss

    jon koss Subscriber

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    I took a gander - it is an Omega condensor head with an Aristo cold light insert.

    Jon
     
  16. jnanian

    jnanian Advertiser Advertiser

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    hi jon

    i have one of these dimmers and i use it pretty often. the aristo cold light that i have is the high output light ( HI ) and they don't kid around when they say twice the light. most of my negatives are a bit thin because i have been using a condensor for the better part of 20 years - so i got the dimmer to help me with my film that isn't fit for a cold light head :smile:

    - - john
     
  17. waynecrider

    waynecrider Member

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    I have a dimmer available as I sold my D2.
     
  18. jon koss

    jon koss Subscriber

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    Thanks - please send a message and let me know the details.

    Jon
     
  19. jon koss

    jon koss Subscriber

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    Wow - under the theory that the best solution, even if it costs a bit more, will pay for itself in saved time and materials, I just took delivery of the Aristo dimmer. Super well built unit. Switching between paper speeds will now be zero headache. Many thanks for all of the suggestions.

    Jon
     
  20. voceumana

    voceumana Member

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    If you can find ND filter in a large enough size, you could cut a circle of it to fit above the diffuser filter. Or, get some grey plastic at a local plastic store & have them cut a circle of it to replace the diffuser.

    If the change needed is small enough, you might be able to get away with a second diffuser disk to cut the intensity.

    Charlie