Experimenting with LED lighting for Durst M605

Discussion in 'Enlarging' started by psvensson, May 21, 2009.

  1. psvensson

    psvensson Member

    Messages:
    625
    Joined:
    Apr 16, 2004
    Location:
    Queens, NY
    Shooter:
    Medium Format
    I thought others considering LEDs for their enlarger heads might find this story useful:

    The halogen bulb burned out in the color head of my Durst M605, so I replaced it with a new 100w "EPJ" lamp, intended for projectors. It worked, but it was too bright for my taste and much brighter than the old, unmarked bulb. I got exposure times of a few seconds at f8 with a 35mm neg enlarged to 5x7 on Kentmere VC (a fairly fast paper). And that was with the diffusor set to the dimmer 6x6 setting.

    So I thought I might experiment with one of the new LED bulbs. I knew it would be less bright, which I wanted, and I also figured that the accuracy at short exposure times would improve, because the halogen bulbs take time to warm up and also glow for a short while after power is cut, whereas LEDs turn on an off instantly.

    I bought a 2W warm white MR16 LED bulb one, said to be equivalent to a 20W halogen. It fit into the socket in the enlarger head with a little wiggling. It didn't burn out the transformer, and the light looked bright to me. But by the time it came through the diffusion box and the optics, it was barely visible on the baseboard - a real lesson in how inefficent the diffusor head is.

    I gave LEDs one more chance. I bought a 4W cool-white bulb, figuring the added blue and overall higher efficiency as compared to warm white would help. It was significantly brighter, but it was nowhere close to bright enough. In fact, it was 9 stops dimmer than the 100W bulb! Filtering the light through a blue filter brought the difference down to about 8.5 stops, but that would still mean unacceptably long exposure times.

    So it's back to halogens for me - I've ordered a 50W bulb. Now, what I really want is to build a head with banks of green and blue LEDs that can be switched independently for split printing ...
     
  2. BetterSense

    BetterSense Member

    Messages:
    3,127
    Joined:
    Aug 16, 2008
    Location:
    North Caroli
    Shooter:
    35mm
    Is this a problem for you? With my 6x6 Omega condenser enlarger I generally print 5x7s from 35mm at f/16 for about 10-20 seconds, through a grade 2 under-lens filter.
     
  3. paul_c5x4

    paul_c5x4 Subscriber

    Messages:
    1,916
    Joined:
    Apr 22, 2009
    Location:
    Ye Olde England
    Shooter:
    Large Format

    I too have been playing around with the use of LEDs. So far, it has just consisted of exposing a few scraps of VC paper to various coloured LEDs.. Calibrating the setup for specific grades is going to be one challenge, getting an even illumination across a 5x4 neg, another.
     
  4. psvensson

    psvensson Member

    Messages:
    625
    Joined:
    Apr 16, 2004
    Location:
    Queens, NY
    Shooter:
    Medium Format
    My lenses are visibly better at f4-5.6, so I generally don't stop down further than f8. But you have a point - on a 5x7 print, the difference probably isn't very big.
     
  5. K-G

    K-G Subscriber

    Messages:
    371
    Joined:
    Mar 29, 2006
    Location:
    Goth, Sweden
    Shooter:
    Multi Format
    LED lighthead

    It may be worth checking this link at the German company Heiland.
    I don´t know what state this lighthead is in right now, but it certainly
    looks interesting. Unfortunately I didn´t find any English translation,
    so you may have to dig out your old German dictionary from the basement.
    Good luck and best regards from

    Karl-Gustaf Hellqvist

    http://www.heilandelectronic.de/html/deutsch/produkte/kaltlicht_main.htm
     
  6. vdonovan

    vdonovan Subscriber

    Messages:
    502
    Joined:
    Jan 8, 2008
    Location:
    San Francisc
    Shooter:
    Large Format
    I was only able to translate the first line: "Sie wollten schon lange Splitgrade® nutzen?" means "Are you one of those Splitgrade printing nuts?"
     
  7. paul_c5x4

    paul_c5x4 Subscriber

    Messages:
    1,916
    Joined:
    Apr 22, 2009
    Location:
    Ye Olde England
    Shooter:
    Large Format
    Thanks for the link - Google/translate gives enough to make sense of the information. Particularly useful is the light density specs.. Blue 0.5cd/cm2, Green 0.7cd/cm2.
    Gives me a ball park figure to aim for if/when I get the soldering iron out.
     
  8. philipp.leser

    philipp.leser Member

    Messages:
    17
    Joined:
    Oct 23, 2008
    Shooter:
    Medium Format
  9. RobertV

    RobertV Member

    Messages:
    1,057
    Joined:
    Mar 8, 2009
    Location:
    the Netherla
    Shooter:
    Multi Format