LED light conversion on Durst Laborator 138

Discussion in 'Darkroom Equipment' started by Tony Egan, Mar 16, 2013.

  1. Tony Egan

    Tony Egan Subscriber

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    Here is a cheap and simple conversion I finished today. I have run a few tests on 6x9 negatives and found no issues with coverage or even-ness of light reaching the paper. I will check 4x5 and 5x7 in the next few days. I estimate this 15w light source is about 1/2 stop brighter than the normal 300W opal globe I have been using, based on one recent negative I tested against. And, of course, the heat emission is negligible.

    I have done a bit more research and found there is a 21W LED generally available with a 90mm cutout which may be a bit brighter. Once you go to 30W or more the units seem to to be bigger requiring a 150mm cutout or larger. It's possible I could just squeeze that size into the housing also. The only tools I needed were an electric drill and a 90mm (3 1/2 inch) hole cutter. The board screws into existing holes on the existing 'L' bracket inside the head and the light is fixed to the board with the standard gimble springs.

    Here is the light I bought:
    http://www.ebay.com.au/itm/261103414375?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

    72 DSCN3379.jpg 72 DSCN3362.jpg 72 DSCN3355.jpg 72 DSCN3357.jpg
     
  2. SMBooth

    SMBooth Member

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    Interesting, FYI the link you give is to 4 units, they do sell single units as well, which I assume you meant to link to.
    I pulled my Durst 1000 to pieces today as the mechanism which allowed me to adjust the head height failed. While it is down I considered converting it to a diffuser type by removing the condenser lens and painting the space white and adding diffuser. I might consider one of these lamps at the same time based on your tests. So get going....

    How deep is the light?
     
  3. bernard_L

    bernard_L Member

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    Last edited by a moderator: Mar 16, 2013
  4. ac12

    ac12 Member

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    Interesting.
    I would want a smaller unit for my L1000. I don't need that much light.
    I like the LED, then I can stop looking for a heat absorbing glass.

    Let us know how it prints w VC paper.
     
    Last edited by a moderator: Mar 16, 2013
  5. Tony Egan

    Tony Egan Subscriber

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    It's 60mm from the back of the heat sink to the back of the board.
     
  6. Tony Egan

    Tony Egan Subscriber

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    Thanks Bernard. I have read through most of these threads on LED conversions and understand there may be variations in contrast with VC paper. I'm not one for agonising over minor technical points relying more on eye and emotion when it comes to printing, but it is valuable to know that not all light is the same colour and I may need to fine tune some filter settings if trying to recreate a past print.
     
  7. Tony Egan

    Tony Egan Subscriber

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    Update: Printed 4x5 and 5x7 over the weekend and coverage is fine with a 150mm enlarging lens used for both. Contrast on VC paper is a marginally harder by about 1/2 to 1 grade based on a small sample. i.e. I find grade 1 1/2 gives me the kind of contrast I was getting using grade 2 or maybe 2 1/2 with the other light source. Very happy with tonal separation and midtones and printing seemed marginally "easier" overall. Maybe it was the lack of heat penetrating my forehead and the absence of that faint burning smell!

    This is a less than perfect way to illustrate results but here are rough shots of two prints from well exposed negatives at grade 1 1/12. Ilford warmtone paper in dektol with 3 mins in selenium. I will stick to this light source for now as I can't see any downsides so far.

    72 DSCN3386.jpg 72 DSCN3385.jpg
     
  8. pcyco

    pcyco Member

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    hallo

    that looks great i think i will convert my 138 also

    thanks a lot and let us know your experiences

    thomas
     
  9. Marco Buonocore

    Marco Buonocore Member

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    Amazing, Tony! Thank you. I've got one of the Atlas bulbs, and I often wonder what I'll do when it burns out. This looks like a viable option.
     
  10. jon.oman

    jon.oman Member

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  11. Tony Egan

    Tony Egan Subscriber

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  12. Tony Egan

    Tony Egan Subscriber

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    Yes, my thoughts exactly. I found one site recently wanting to sell the large 300W replacement globes for Durst 138 for $250 or more. No Thanks!
     
  13. jon.oman

    jon.oman Member

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    I believe it is 100W. I'll have to look at the owners manual....

    Thanks for the link, that may work as well!
     
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  15. pcyco

    pcyco Member

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    hallo

    i have done it :smile:

    i replaced the opalbulb with a led spot (app. 15 watt).
    i dont know the lumen i dopnt know the ligtcolour but it works very well.

    my spot had no diffusor so i used a milkwhite plexi-glass.

    no brightness falloff to the borders.

    with 4x5 i have enough light (10 sec for 13x18 cm)
    but for 24x36 mm i have to expose the baper for 13x18 cm about 30 seconds.

    --
    thomas
     
  16. Tony Egan

    Tony Egan Subscriber

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    Hi Thomas - thanks for your contribution. 30 secs is still pretty good in my experience. With Ilford warmtone paper I was previously in the 60-90 seconds range for 120 and 4x5 film on 11x14 inch paper. This has come down to around 30-45 at similar apertures (f11-f16) after my conversion. It's good to see a positive influence from changing technology on our world. I'm now thinking about building an 8x10 enlarger using LED lights.
     
  17. pcyco

    pcyco Member

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    hallo

    yes it was good to see that we schould not only look at curves and measurements of the light-physics. just try it and lets see what happens.
    an other point for me to try it with any led-lamp was that some films have other basecolors (foma - blue) this also must have an influence at the printing but nobody cares.

    next thing ist to get a stronger light and building an diffusor head.

    regards

    thomas

    edit 2 examples
    2013_04_03_TRAUBENw.jpg
    2013_04_03_RINGw.jpg

    the ring is 4x5
    the grapes are 24x36
    both printed on kentmere vc 23x18 cm glossy
    the grapes filter 0
    the ring filter 4
     
    Last edited by a moderator: Apr 3, 2013
  18. MartinP

    MartinP Member

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    This idea of using the downlight/spotlight things is great and I/m now thinking of a high-power version of a Varicon head.

    However, I'm wondering about the distance from the condenser (via the mirror) -- shouldn't the illuminated surface be on the former centreline of the bulb, in order to be concentrated optimally by the condenser(s) ? With any luck there is so much light power available that this isn't a problem, but it might make a difference at extremes.

    I'm also curious about the turn-on delay of the unit. Does the enlarger keep the bulb on all the time and have a shutter for exposures?
     
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  19. pcyco

    pcyco Member

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    hallo

    the worst thing is the diffusor (plexiglass).
    i think it absorbs to much light i think i will look for something thinner. any foil etc. thinner and less absorbing light.
    @ martinp: yes i have located the laamp in the axxis of the lighthole with the heatabsorbingglass. aprox. 3 cm away from the diffusorplexi in the filterdrawer.

    --
    thomas
     
  20. MartinP

    MartinP Member

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    Thank you for the useful information Thomas. My wondering about the light location was for the OP in Australia! The location of the lamp in his big Durst is further away from the condensers than the usual lamp position, though it still works :smile:
     
  21. Tony Egan

    Tony Egan Subscriber

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    Hi Martin - the bulb position could be moved as it is mounted to the same metal track to which I have mounted the LED. I'm not an expert on the physics of light dispersion although I wondered myself about this as the opening which used to hold the heat resistant glass (I removed) is much smaller than the mirror and the 5x7 inch maximum format. My test was to expose a piece of zone 5 negative at various times to check for light fall off at usual working apertures. I could not see any with 6x7cm or 4x5 inch formats. My amateur hypothesis is the LED may be more precise and uniform than a bulb as the light is coming from a broader source of LED units from a flat field as compared to the narrow filament of a bulb through a curved surface?

    As Thomas also indicated, I was quite precise with the LED mounting hole on the board using a spirit level to ensure the LED was exactly aligned to the square opening in the lamp housing. You can see some of my pencil marks on the board in the photo.
     
  22. Tony Egan

    Tony Egan Subscriber

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    Re the turn on delay, yes there is a fraction of a second delay but much less than dry down effect so not something I agonise over! It is not unusual for variations in the mains supply to visibly change the light output from the bulb in any case, so I think the output from a 12v source may in fact be more consistent. I make a small adjustment to my starting exposure on the first print based on the number of exposures on the test strip but I think this is immaterial given my final print is usually version 4 or 5 after time and contrast adjustment, dodge, burn etc etc.

    There is no shutter. Light goes on and off via an RH timer in my case.
     
    Last edited by a moderator: Apr 3, 2013
  23. MartinP

    MartinP Member

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    Thank you for the extra info. Since I posted (of course!) I have found there are different LED-driver modules which have different startup times, so you have wisely chosen a quick one.

    Actually, I'm not completely sure that the heater element in my kitchen-grill uses any more power than that 300W bulb in the original Durst head :wink:
     
  24. doughowk

    doughowk Subscriber

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    Any problem with converting a Pavelle Color light head that's for a Durst L1000 into using LED light(s)? I have two of the heads, and was thinking of converting the current spare. It sure would be quieter in the darkroom without the fan running ;-)
     
  25. gliderbee

    gliderbee Member

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    I don't know the proper word in english, but I use a piece of paper that we would call (translated) "chalk paper". It is also used to copy a picture or drawing by following it with a pencil; it's semi-transparant. Works very well and does not take too much light away (about one stop).

    Stefan

    Verstuurd van mijn GT-P7510 met Tapatalk
     
  26. MattKing

    MattKing Subscriber

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    In English, it is known as "tracing" paper.