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Thread: High power LEDs

  1. #11
    Jon King's Avatar
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    Quote Originally Posted by Pragmatist
    Has anyone used these led's to replace the bulb in a conventional condenser head? I am thinking that this might be practical. Any thoughts?
    A project of mine, stalled for a good bit, is to make a 5x7 LED head for a Durst 138 using Luxeon LEDs (lumileds). I've built a basic one to test the concept, and it works quite well. I'm using green and blue ones for a VC head with a few red to add light for focusing. Seperate green and blue LEDs are more efficient than using white, especially for green light, and the filtering can be done with the controller, rather than filters
    Jonathan
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  2. #12
    MurrayMinchin's Avatar
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    Quote Originally Posted by Jon King
    A project of mine, stalled for a good bit, is to make a 5x7 LED head for a Durst 138 using Luxeon LEDs (lumileds).
    Did you use Blue or Royal Blue, and what grade would you estimate they gave you in contrast? I hear getting a soft grade of contrast is no problem, but getting a hard grade is, well, hard.

    Murray
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    Note to self: Turn your negatives into positives.

  3. #13

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    Quote Originally Posted by RJS
    I think Paul Butzi mentioned an LED safelight on his web site. I tried to find the maker and couldn't. Maybe you'll have better luck. It sounded terrific!
    Calumet makes an amber LED safelight. they work great. cost about 149 dollars but good for 100,000 hours. I recommend them.

  4. #14
    Jon King's Avatar
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    Quote Originally Posted by MurrayMinchin
    Did you use Blue or Royal Blue, and what grade would you estimate they gave you in contrast? I hear getting a soft grade of contrast is no problem, but getting a hard grade is, well, hard.

    Murray
    I used royal blue.. The first referenece I saw on the internet was the light source by Huw Finney. If I remember he used blue, because the royal blue was not available at the time. The royal blue wavelength seems to be a better match to Ilford MG paper at least

    I made a 6x7 source with 2 royal blue and 2 green. For a larger head.. I'd change the ratio of green to blue.. I have notes but forget which way off hand. I printed some prints, mostly to check out different mixing box schemes, and didn't actually measure the grades I was getting.

    I use a single 1 watt red lumiled as a safelight in a bathroom/temp darkroom.. I'm guessing two would be needed the permanent room I'm working on which is the main cause of the delay in the light source.
    Jonathan
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  5. #15
    MurrayMinchin's Avatar
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    Thanks Jon. Huw's site is the one that got me thinking as well...

    Murray
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    Note to self: Turn your negatives into positives.

  6. #16
    Robert Hall's Avatar
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    Thanks Guys.

    I would use red for the safelight. The others tend to fog Forte fairly quickly.

    My darkroom is huge, 800 sq feet. I've loved my Thomas safe light, but it fogs the Forte. It seems that the Ilford can be printed with the safe lights on full and still make a great print. (yes, I understand the physicis of it all, it's still weird!)

    I will give some of the ideas a try. And it's a good thing I'm an electrical engineer as well, what self respecting photographer would know what a MOSFET is?

    Here's to brighter days!
    Robert Hall
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    Technology is not a panacea. It alone will not move your art forward. Only through developing your own aesthetic - free from the tools that create it - can you find new dimension to your work.

  7. #17
    Bob F.'s Avatar
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    Quote Originally Posted by Robert Hall
    Thanks Guys.
    <snip>
    I will give some of the ideas a try. And it's a good thing I'm an electrical engineer as well, what self respecting photographer would know what a MOSFET is?

    Here's to brighter days!
    You'd be surprised - judging from other threads and the "What do you do for a living" one, there's quite a few MOSFET huggers on here!

    You might want to try the red-orange Lumiled with the Forte rather than red (I dislike red safelights: I keep hearing SONAR pinging noises in my head and expecting a bloke with a serious beard and roll-neck sweater to pop his head around the door and say something cryptic about periscopes and code books...). At 617nm wavelength, they should be far enough away from the paper's sensitivity. I use amber (590nm) with Ilford and Kentmere VC happily - not tried Forte.

    Cheers, Bob.

  8. #18

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    Quote Originally Posted by Jon King
    I'm using green and blue ones for a VC head with a few red to add light for focusing.
    Has onyone thought of having a few red LEDs in the head and then leaving them always on so that one could see where to place dodge and burn tools before the blue/green light exposure begins?

    Kirk - www.keyesphoto.com

  9. #19
    Jon King's Avatar
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    Quote Originally Posted by Kirk Keyes
    Has onyone thought of having a few red LEDs in the head and then leaving them always on so that one could see where to place dodge and burn tools before the blue/green light exposure begins?

    Kirk - www.keyesphoto.com

    I was planning to put some in my final head.. more to set up the negative with a more 'white' light.. hadn't though of it for dodge/burn..... guess it shows i've never used an enlarger with a red filter under the lens.. huh?
    Jonathan
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  10. #20

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    Quote Originally Posted by Robert Hall
    Thanks Guys.
    I would use red for the safelight. The others tend to fog Forte fairly quickly.

    My darkroom is huge, 800 sq feet.
    Hi Robert,

    If your darkroom is huge you could use the luxeons - especially if as Bob has suggested you add a dimmer. Try a 1W version first and see how you go. My 'darkroom' would be lucky if it was a tenth of your size and the normal 'bright' LED's work fine and are significantly cheaper. Go with the red if you've had paper fogging problems but there's no reason why you can't also add a switched orange/amber as well. I do Lith printing and process ortho film so I use a red safelight and keep it as dull as possible.

    Cheers,
    Roger.

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