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  1. #11
    Curt's Avatar
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    I would appreciate anyone's thoughts on this. The commercial market has not jumped on this, Philip's, (Luxeon) was not all that thrilled at my application for the LED's. But...
    They, Philip's, were not supportive at all when I approached them about my application some time back. "It can't be done in that small of a space, the heat sinks are too large" I'm not sure what the thinking is on there part but I got the message.

    When I receive feedback like that it just makes me more determined to make one for myself.
    Everytime I find a film or paper that I like, they discontinue it. - Paul Strand - Aperture monograph on Strand

  2. #12
    Steve Smith's Avatar
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    I occasionally do some work for a local PA hire/Sound Reinforcement company. They have recently branched out into supplying staging and lighting too.

    Some of their lights are LED such as these: http://www.djempire.co.uk/product/pr...d-light-silver

    Ignore the price listed, they can get me one of these for £34 ($68). I am going to get one to experiment with. I think with the right diffusing it would work fine.

    It has arrays of red, green and blue LEDs and is bright enough for stage use so it would easily be bright enough for an enlarger. In stage use it takes the place of a 500 watt incandescent lamp. however, I would say that it equates more to about 300 watts than 500. Obviously, that's in white mode with all three colours on.


    Steve.

  3. #13
    Steve Smith's Avatar
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    Quote Originally Posted by Curt View Post
    When I receive feedback like that it just makes me more determined to make one for myself.
    Me too. If someone tells me something can't be done or that I can't do it. That's a challenge!


    Steve.

  4. #14
    RH Designs's Avatar
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    Quote Originally Posted by Steve Smith View Post
    It has arrays of red, green and blue LEDs and is bright enough for stage use so it would easily be bright enough for an enlarger. In stage use it takes the place of a 500 watt incandescent lamp. however, I would say that it equates more to about 300 watts than 500. Obviously, that's in white mode with all three colours on.
    Looks interesting Steve. However, "ordinary" blue LEDs aren't really blue enough for best results - I've only been able to get a maximum grade of about 3.5 with them. The so called "royal blue" ones are better, but less easy to find.
    Regards,
    Richard.

    RH Designs - My Photography

  5. #15
    Steve Smith's Avatar
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    I think I may be able to try this out for free. My friend has a couple of these lights where about six of the green LEDs have stopped working. I expect that they are connected in series in sets of six.

    Grade 3.5 would be o.k for me but not ideal. Is grade 3.5 achieved with the blue LEDs only (no green)?



    Steve.

  6. #16
    RH Designs's Avatar
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    Quote Originally Posted by Steve Smith View Post
    Grade 3.5 would be o.k for me but not ideal. Is grade 3.5 achieved with the blue LEDs only (no green)?
    Yes. I was using single 10W LEDs rather than an array, as I only need to cover 6x7 and they fitted neatly into the mixing box of my LPL 7700. This was a quick experiment which I had to abandon due to time constraints, but I intend to revisit in the future.

    Extreme contrast ranges on Ilford MG4 RC were approx 2.5 stops (ISO(R) 75, grade 3.5) with blue only and about 6 stops (ISO(R) 180, grade 00) with green only.
    Regards,
    Richard.

    RH Designs - My Photography

  7. #17
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    The saga continues!!!! I bumped the Hard contrast range into Grade 5 by adding 4 1watt, near UV/Violet LED’s, (400nm). (See the grid attached for placement.) I ran step wedges to test the contrast. I used Ilford MGIV RC. Looks like I am getting about ISO 65, so well into Grade 5. (See wedge attachments.)

    VC paper was designed for tungsten light sources and is sensitive to below 400nm wavelengths, that is, sensitive to UV light. Tungsten and fluorescent light are broadband and extend into the UV range. The very tight spectral response of the LED’s requires more thought to the paper sensitivity and contrast range. One of the concerns in using LED’s was the inability to get to Grade 5. The Phillip’s Royal Blue produced the hardest contrast, but, in my tests, only got into the lower Grade 4 range.

    We all must be concerned with using the near UV wavelengths. There are some basic safety procedures to avoid issues. Do not look directly at the lit LED, even for a few moments. The spectrum of these LED’s is very narrow with the peak at 400nm. This is really violet and the short wavelength at which light is normally categorized as “visible” for the human eye. But never forget that you only have 1 pair of eyes and always proceed with due caution

    The Soft Grade is very extended, about ISO 215, Grade 00 with MGIV RC. I will run some tests with non-extended range papers, as well. I am using a 21 step wedge. I would like to try a finer gradation, as I narrow down the spectral response.

    The Hard is now about .5 stops faster than the Soft. I may try to achieve a better balance by removing some of the Royal Blue LED’s. Although the near UV LED’s are not “as powerful” , in wattage, the shorter wavelengths are higher in energy.

    The head is really nice to print with, fast, quiet and cool! The elimination of the fan noise and the head heat is a true joy. I did not realize how much I had “environmentally internalized” all that goes with pouring 1000 watts of mostly heat into the DR.

    I have ordered some small modular boards that use the new SMD Rebel LED’s. This will allow easier scalability. The work continues and the LED budget starts to look like the current US Federal budget!
    Attached Thumbnails Attached Thumbnails G+B Ilford MGIVRCweb.jpg   G+BV Ilford MGIVRCweb.jpg   LED Grid UV web copy.jpg  
    Last edited by galyons; 08-02-2008 at 11:52 AM. Click to view previous post history.
    But your flag decal won't get you into Heaven any more. They're already overcrowded from your dirty little war.
    Now Jesus don't like killin' no matter what the reason's for, and your flag decal won't get you into Heaven any more. – John Prine

  8. #18

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    Very nice. Did you consider using the Luxeon Star LEDs instead of the bare leds? I find the stars much easier to solder and work with. I hope using the resistor works ok for you. I would be concerned about temperature and voltage fluctations affecting consistency. A simple constant current drive circuit like one of these might be worth it for the piece of mind.

  9. #19
    jeroldharter's Avatar
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    galyons,

    Are you still using this 8x10 light source? How is it going? Just curious.
    Jerold Harter MD

  10. #20
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    This is amazing! This is the last thing I thought might be possible:o

    Do you actually get even light and 2.75 more stops.. :o

    I have 2 Durst's, a 138 and a 184.

    dw


    Quote Originally Posted by galyons View Post
    Well after about 2 months of toasting $3 Luxeon III LED’s like they were popcorn, I have successfully completed the conversion of a Durst 184/301 head to LED light source.

    Firstly, a big “Thank You” to Huw, whose site and emails helped me to get started. His DeVere 504 conversion was my inspiration. I modified Huw’s layout to accommodate my 10”x10” Durst head and used Luxeon III’s, rather than Luxeon I’s.

    My printing process is pretty much some graded and mostly VC. For VC, I use the split grade technique utilizing a RG Designs StopClock. So my design elements were SoftMax and HardMax as simply as possible. What a joy, no more “spinning the dials” on my color head. Just flip 1 toggle for Soft, green, 1 toggle for Hard & Graded, (blue), both for focusing.

    My previous 8x10 working head, a 1000 watt quartz halogen dichroic, worked very well. Quartz halogen lamps produce most of their light in the red range combined with copious amounts of heat. I was looking for a simpler interface, less heat and less noise, (fans), So the comparison, easy, minimal heat and perhaps, no fan needed.

    What about illumination efficiency? The LED head is 2 ¾ stops FASTER! That makes the LED’s illumination equivalent to my old head with 2750 watts. Think about it. It would take 11 quartz halogen lamps and 2 ¾ time the heat to generate the same hard/soft printing power!

    The Durst head was really a joy as a base platform for the conversion. Lot’s of room in the fan compartment for the 24 volt power source and wiring harness runs. I left the internal fan in place, just in case I need to dissipate some heat faster than my heat sinks alone will accomplish. It has 10x10 and 5x7 mixing boxes that slide in like big drawers. Take the mixing box out and the led panel is readily accessible.

    I am still sorting things out, but the initial testing and process run was very, VERY encouraging.

    I will post more as I get more experience with the new LED head, but so far, I’m sold.

    Cheers,
    Geary

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