LED Bulb in Condenser head

Discussion in 'Darkroom Equipment' started by ParkerSmithPhoto, Feb 14, 2012.

  1. ParkerSmithPhoto

    ParkerSmithPhoto Subscriber

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    Has anyone experimented with a LED Bulb in Condenser head to avoid heat and popping. Or maybe a compact fluorescent? Any issues with the spectrum for VC papers?
     
  2. dehk

    dehk Member

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    I know one problem with a compact fluorescent, it has to warm up. I'm interested to hear about using a LED bulb as well.
     
  3. Mainecoonmaniac

    Mainecoonmaniac Subscriber

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  4. MattKing

    MattKing Subscriber

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  5. Roger Cole

    Roger Cole Member

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    Yep. As I said in that thread, I bought one of these. That was right after my last printing session and busy weekends have kept me from trying it. I have a three day weekend coming up this week though and lots of negatives to print, so I'll be trying it out. I'll report back here.

    It is a very well made piece of gear.

    Parker, if you're really interested in getting one I might be persuaded to sell that D2 back to you (minus the grain focuser which is a huge improvement over my old one!)
     
  6. Laurent

    Laurent Subscriber

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    Thanks (millionS of them) for the link. I'm using a similar setup but did not drive so many tests (I'm only using white LEDs).

    My enlarger is a Priox, the setup works fine (my difuser is baking paper, I have to test some material they use in theaters. The white plexi cost me too much (3 stops)).
    My only issue is converage on the edges for 4x5 but I'm afraid this has to do with my enlarger (it's a 9x12 one)
     

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  7. cardiomac

    cardiomac Member

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    Try 1/8" #2447 white acrylic. It cuts only 50% (1 stop). If you can see the LED's themselves through the acrylic, try wet sanding the surface closest to the LED's to create a ground glass effect. Alternatively, try the 3/16" sheet which cuts 58% of the light. eStreet Plastics (www.estreetplastics.com) is a good source of acrylic in small quantities.

    Also, make sure to consider proper thermal management when using LED's. Overheating dramatically shortens their life and significantly lowers their light output.
     
  8. cardiomac

    cardiomac Member

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    The problems with commercial LED replacement bulbs in a condenser lamp house are multiple. Firstly, the condensers are designed with a round, even light source in mind. Any deviation from evenness or size will manifest as unevenness in light at the easel. Secondly, to keep the bulb in focus the distance to the condensers must be maintained as it was with the original incandescent bulb; most commercial LED's are shorter or longer than the bulbs they replace. Thirdly, LED replacement bulbs have low light output, far less than a typical 150 watt incandescent enlarging bulb, and the light may come out of the bulb directed squarely at the lamp housing, where it is wasted, rather than toward the condenser where it can be directed at the negative. And finally, commercial LED replacements are poor at thermal management, especially in the confines of a condenser lamp house. This manifests as unsteady light output during an exposure and a dramatic shortening of the bulb life span.

    It was to overcome these problems that I designed my own LED lamp house. Unfortunately, as you know, it is available only for the Omega D series enlargers at this time.
     
  9. Laurent

    Laurent Subscriber

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    I'm looking for one of these diffusers (I contacted Kinght Optical, who seem to make what I need http://www.knightoptical.com) but in the meantime I decided to bite the bullet and I doubled the LEDs in my head.

    I arranged them in a larger rectangle, with more density on the edges, hoping this will help in illuminating the corners and edges.