LEDs as enlarger light source

Discussion in 'Darkroom Developing and Printing' started by G.P, Dec 1, 2003.

  1. G.P

    G.P Guest

    I was doing some GOOGLE searches on LEDs to build a "poor-man's ZeeG-align"
    and I am now wondering if anyone has experimented using white light LEDs to
    replace the light source of enlargers? Heat could be greatly reduced,
    perhaps eliminating the need of a fan in a Omega Dichroic II head (for
    instance). For what I have read, there are also LEDs "bulbs" that would
    screw in on regular bulbs sockets, meaning a condenser incandescent light
    bulb could also be replaced by LEDs. Comments?

    Guillermo
     
    G.P, Dec 1, 2003
    #1
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  2. Well, the shape of the light source is radically different, and very tiny; I
    don't think it would be a screw-in-the-bulb kind of conversion. But a
    white-LED cold-light head ought to be a very fine thing: instant-on,
    constant brightness, very little heat. Somebody needs to invent one!
     
    Michael A. Covington, Dec 1, 2003
    #2
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  3. G.P

    Jorge Omar Guest

    There was a guy in the NET (IRC his name was Hun or Hus) that did a Vc head
    using blue and green LED's (high power Lumileds).

    Unfortunately, his site is gone and I've erased the bookmark.
    But if someone is interested, I have a circuit he sent me (but I feel it's
    incomplete)

    Jorge
     
    Jorge Omar, Dec 1, 2003
    #3
  4. G.P

    Dana Myers Guest

    What does the spectral energy of a "white" LED look like?

    Dana
     
    Dana Myers, Dec 1, 2003
    #4
  5. G.P

    John Guest

    Are you sure you don't mean Tim Shoppa ? His site is at ;

    http://www.trailing-edge.com/~shoppa/led.html

    IMO, it has wonderful possibilities but the cost isn't exactly low. Also I
    have to wonder how much light output a bank of LED's can have.

    BTW, the new high-output LED's are having a significant impact in lighting
    today. Here's a link to a site that sells replacement lamps for incandescents
    rated up to 200W.

    http://members.shaw.ca/sagelighting/led_spotlights_and_bulbs_specifi.htm

    Regards,

    John S. Douglas - Photographer, Webmaster & Computer Tech
    Please remove the "_" when replying via email
    Website --- http://www.darkroompro.com
     
    John, Dec 1, 2003
    #5
  6. My guess is that there's about to be a very big revolution in lighting
    generally. The humble incandescent light globe produces more heat
    than light and has to be replaced after 1000 hours or so. LEDs last
    for decades, so the marketers in the lighting industry will have to
    come to grips with that somehow. (Although I have noticed that LEDs in
    car tail and brake lights are starting to exhibit "industry standard"
    failure rates- trust the car industry)

    Back to enlargers: There was a thread somewhere and someone was
    selling tri-coloured LED arrays for enlargers. For VC use, two would
    be enough- green and blue. The trick would be to get uniformity,
    shouldn't be too hard when you look at curved cold light tubes working
    well. Intensity needs to be regulated, and there was a thread in
    which someone had worked out a sophisticated circuit with intensity
    feedback. LEDs vary in intensity, so maybe they'd have to be matched
    (like power amp transistors in the old days)

    Interesting topic. Let's hear from the engineers.
     
    John Stockdale, Dec 1, 2003
    #6
  7. G.P

    John Walton Guest

    The spectrum can be found on any of the manufacturer's data sheets -- try
    Agilent for a starter, Lite-on, Panasonic etc.
     
    John Walton, Dec 1, 2003
    #7
  8. G.P

    Jorge Omar Guest

    Google found the site, but with a new URL:

    http://huws.org.uk/

    But Tim Shoppa's article may be better for a condenser enlarger (I use
    some like it as a red safelight).


    Jorge
     
    Jorge Omar, Dec 1, 2003
    #8
  9. G.P

    Jorge Omar Guest

    Forgot to add:
    I exchanged some emails with Huws, and the 1W lumiled is bright enought
    for normal times exposures.

    Jorge
     
    Jorge Omar, Dec 1, 2003
    #9
  10. G.P

    Jorge Omar Guest

    1 - It may be more expensive to implement, but forget about changing
    lamps for your lifetime.
    2 - Yes, intensity regulation would be a nicety - and fairly cheap to
    implement.
    3 - Since there will be (a lot?) of light diffusion, they do not have to
    be matched.
    4 - Each color string shall be series connected or the circuit will
    become undully complex.

    Now, all that's missing is a soldering iron...

    Jorge

    (John Stockdale) wrote in
     
    Jorge Omar, Dec 1, 2003
    #10
  11. One would think so.

    To rain on the parade -- LED's don't have constant light output: they drift
    with time for the first few months of on-time, LED-LED consistency is
    the pits, they drift with temperature and they take 5+ minutes to stabilize
    after they have been turned on as that the junction temperature stabilizes.
    They _do_ generate heat (though they don't radiate it as a hot lamp
    does) and are not very efficient. Oh, and the light output is slightly
    polarized just for extra joy.

    There is ought without a dark lining.
     
    Nicholas O. Lindan, Dec 1, 2003
    #11
  12. _Very_ nice piece of work.
     
    Nicholas O. Lindan, Dec 1, 2003
    #12
  13. G.P

    John Guest

    Right up there with flourescents then. Anyone ever put a shutter in an
    enlarger that didn't have one from the factory ?

    Regards,

    John S. Douglas - Photographer, Webmaster & Computer Tech
    Please remove the "_" when replying via email
    Website --- http://www.darkroompro.com
     
    John, Dec 1, 2003
    #13
  14. G.P

    PSsquare Guest

    Seems alluring at first blush, but given the technical hurdles already
    identified, I don't see where the declining market for conventional film
    based enlargers would ever justify more than a meagre investment if any at
    all. One of the first questions fore any new technical product is "Is the
    market real?" Film based enlargers are a declining market. The answer
    should be "No, the market is not real for a new light source in enlargers."

    Just my thoughts.

    PSsquare
     
    PSsquare, Dec 1, 2003
    #14
  15. A valid, and often profitable, business strategy is to go after an
    increasing share of a declining market.

    If one can accumulate share faster than the market declines then one
    has a growth business.

    Given enough time, the market for most anything will turn around due
    to increased demand from an increasing population and from
    3rd world markets coming on line.

    Here in Ohio we have an expanding market for buggy whips, what
    with the Amish and the country yuppies.

    In the end everything dies: Capturing the market for slide-rules
    is probably a dead issue for the foreseeable future.
     
    Nicholas O. Lindan, Dec 1, 2003
    #15
  16. G.P

    Jorge Omar Guest

    Dam! and I was intending to sell my mint Hemi hyperbolog at a premium!

    ((-:

    Jorge
     
    Jorge Omar, Dec 1, 2003
    #16
  17. G.P

    Dana Myers Guest

    My real point was that any light source needs to be evaluated for
    spectral compatibility with the photosensitive materials in use,
    and a visibly white LED might not be anything near truly white.
    If I understand white LEDs correctly, they're either UV emitters
    exciting a flourescent layer or they're monochromatic visible emitters
    exciting a flourescent layer to broaden the perceived spectrum.

    So, not all types of white LEDs strike me as equal.

    Dana
     
    Dana Myers, Dec 1, 2003
    #17
  18. G.P

    Jorge Omar Guest

    I would not use a 'white' LED for color photos without a good test first.

    Jorge
     
    Jorge Omar, Dec 1, 2003
    #18
  19. G.P

    John Walton Guest

    Is that a 426 Hemi Hyperblog ?

     
    John Walton, Dec 1, 2003
    #19
  20. G.P

    Jorge Omar Guest

    No, it's a 255D - bamboo, 12 inches

    Jorge

     
    Jorge Omar, Dec 1, 2003
    #20
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