Using LED bulbs in an enlarger.... GREAT!

Discussion in 'Darkroom Equipment' started by Ron789, Jul 7, 2017.

  1. Ron789

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    Recently I started experimenting with the use of LED bulbs in enlargers. After some trial and error it now works great for me!

    I've noticed previous threads on this subject with different findings. I guess the LED bulb technology is still advancing so let me share my recent findings:

    I use Osram Parathom 4000K LED bulbs, 5 watt and 10 watt.
    I tried 2700K and 3000K bulbs and other brands but those all failed for me. The contrast at higher grades was too low: a grade 5 print with a 2700K or 3000K LED bulb was equal to a grade 3.5 print with a traditional bulb (Philips Photocrescenta 150w). A Philips 3000K bulb produced less contrast than an Osram 2700K bulb... strange.
    The contrast with the Osram Parathom 4000K is really the same as the Philips Photocrescenta traditional bulb, across the entire 0-5 range.
    What amazes me is the amount of light: the 5w and 10w LED bulbs produce much more light than the 150w Philips bulb, resulting in much shorter exposure times. Yesterday I printed a 20x24" (50x60cm), using a Leitz Focomat 1c, Focotar-2 lens at F/8, grade 5 filter, Ilford MG FB WT, Osram 10w LED bulb, exposure time 40 seconds. Less than half of what I needed with the Philips 150w bulb.
    The light spread of the LED bulb is fine.
    I also used the LED bulb in a Focomat 2c and here again the results were excellent.

    The advantages of using such LED bulbs are obvious: cheap, easy to purchase, no heat production (!), shorter exposure times.
    I'd be interested to hear what other experience using modern LED bulbs in enlargers.
     
  2. Speed Gray

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    So where did you purchase them?
     
  3. mshchem

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    Definitely much less heat, Do you have normal contrast without filters? Heiland makes fancy splitgrade LED heads, RGB leds, for big money. Makes you wonder if someone could make a RGB single bulb, control with a cell phone app. That would be cool.

    Are you using filters under lens or in a filter drawer?

    Sounds like a good approach, Best Mike
     
  4. OP
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    Ron789

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  5. OP
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    Ron789

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    I never work without filters. In the Focomat 2c I use the filter drawer, in the Focomat 1c under the lens. makes no difference.
     
  6. Anon Ymous

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    Ron, did you consider 5500K leds? These would, in theory, give you higher contrast than the 4400K ones.
     
  7. OP
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    Ron789

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    I did not try anything above 4000K. Isn't the contrast grade limited by the paper? I would expect that the paper does not respond to the light above a certain color temperature. But it's an interesting question. I'd be interested to hear if someone has any experience with this. Would a 5500K LED enable us to print at grade 6 or 7?
     
  8. Anon Ymous

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    Good question Ron. I suspect that the paper itself does have a maximum contrast, but the filters don't have a very sharp cutoff region. That I assume is the reason that the same filter can produce different results with different light sources. Of course, I could be wrong... But anyway, a grade 7 or 6 sounds a bit of a stretch.
     
  9. Tony Egan

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    Hi, my experience in this thread.
    (there was a url link here which no longer exists)

    The ebay link is now obsolete and there have been many advances in LED lighting since that thread. That light measures around 4300k using this handy app:
    https://itunes.apple.com/us/app/lightspectrum-pro/id468368751?mt=8

    I have since converted a Beseler 45m into an 8x10 enlarger using 4 LED globes as a light source. It's a bit clunky but it works!
     
  10. mgb74

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    The printing on the bulb (assuming there is some) did not cause any issues?
     
  11. David Brown

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    While I am convinced led bulbs are the future, we're still in a transitional phase of the technology.

    My experience with all types of led bulbs is that there is often a slight delay in both coming on and going off. As exposure times get longer, the effect of any delay would fall off exponentially. However, you mentioned that one of the advantages (to you) was shorter exposure times. So, has the delay - if any - of the leds been a factor?
     
  12. OP
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    Ron789

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    No, there is no print on the bulb.
    Modern LED bulbs switch on and off very fast, typically within tenths of seconds. Osram states in the technical documentation of this bulb that the start-up time is <0,5 sec and the time to reach the final color temperature is <1 sec; I guess those times are on the safe side. With any exposure time more than a few seconds these switch on - off times quickly become insignificant. In my testing I worked with exposure times ranging from 2 to 40 seconds and I did not experience any problem.
     
  13. Doremus Scudder

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    The filter determines the wavelengths (color) of light that hits the paper. If there's enough of a particular color bandwidth in the light source, then the appropriate filter will pass it to the paper. If the OP is getting good printing times and contrast with a grade 5 filter, then the paper is probably getting the right dose of the shortest wavelengths it is sensitive to and there's likely no advantage to using a higher-color-temperature bulb. Switching to a higher color temperature will only shorten printing times, not increase the contrast. The problem comes when there is not enough of the deep blues being emitted from the bulb, making printing times long with a #5 filter and only exposing at the long wavelength end of the filter, thereby reducing contrast. To see if the particular LED bulb the OP is using is emitting enough "high-contrast light," one could mount a #47 filter (blue tri-color filter, which is about as blue as VC paper will respond to) and see if the printing times are realistic. If so, then the 4400K bulb is doing just fine.

    Best,

    Doremus
     
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  15. ac12

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    One consideration is the enlarger.
    • If the enlarger configuration is such that the light path axis is out of the TOP of the bulb, that works for the LED bulbs that I have seen.
    • But if the enlarger configuration is such that the light path axis is out of SIDE of the bulb (like Durst enlargers), that could be a problem. All of the LED bulbs that I have seen, have a plastic base on the lower section of the globe part of the bulb. So the illuminated bulb is not a nice circle. What will that do to the evenness of the illumination?
     
  16. OP
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    Ron789

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    Very good question! I had not tried that since my Durst L138s has an Ilford Multigrade 500 head. But your question made me curious so I took off the Ilford head and placed the LED bulb in the Durst. I was expecting uneven light since the LED bulb, seen from the side, is indeed only half a circle.
    It works better than I expected. After careful udjustment of the bulb (which the L138s does just perfectly and very easily with its 3-dimensional adjustment knobs) the light spread turned out OK.
    I measured the light spread for 5x7", with a 210 mm lens and 2 Latico 240 condensors: the light fall off from center to edges and corners was more or less equal to what I measured with a Photocrescenta bulb, and very symmetrical.
    I also measured it for 4x5", with a 150mm lens, Latico 240 and Latico 200 condensors: very similar results. Not perfect and not as even as the Ilford head but good enough for normal printing and very similar to using a traditional Photocrescenta bulb.
    These results quite surprised me since the bulb is not a full circle and also much smaller than the bulbs Durst recommends for this enlarger. But the L138s has very good adjustment possibilities; simpler enlarger typically have more limited bulb movements so there the size and shape of the LED bulb might cause problems.
     
  17. Robbie Bedell

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    Has anyone located this bulb (or equivalent) in the USA. I have been Googling around and can't seem to find anything. I am very interested!
     
  18. ac12

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    Ron,
    If that works, and I can find a G30 LED bulb to work in my Durst L-1000, then the box of G30 bulbs that I got for my Durst L-1000 can be given away.
    The LED bulb would be MUCH cooler than the incandescent G30 bulb.
    Although the opposite could be said, just use the G30 bulbs that I already have, and forget about the LED bulb that I would have to buy.

    Maybe I could find an LED bulb for my M-600 :smile:
     
  19. jon.oman

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  20. Robbie Bedell

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    Thank you Jon! I will get one.
     
  21. ~andi

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    Interesting. I was researching those industrial grade light sources a while back and ditched the idea because of the proportionally high drawbacks compared to what is to be gained. This was one or two years ago and i've not kept track of recent LED developments, so some questions arise:

    1. how stable is the light intensity (brightness/lumen) and spectral uniformity? :

    - over longer time, say one month daily printing (afaik LEDs lose up to about 1/3rd of their luminosity in the first couple of hours burn time)
    - during exposure (short on times)
    - with mains voltage fluctuations

    2. how many on/off cycles before they fail?

    3. when they fail, can they be repaired?

    4. when you say it's cheaper, does this include the environmental footprint? I can get a tungsten bulb which is a little bit of glas, some tungsten and a bit of common metal in a cardboard box for around 5 Euros (probably manufactured locally too).
     
  22. OP
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    Ron789

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    The technical specs of this LED bulb state:
    Average life time: 15000 hours
    On/off cycles: 100000
    Light flow at end of life cycle (i.e. after 15000 hours): 70%
    Start-up time < 0.5 sec

    Repairing a 5 Euro / 5$ bulb after a life of 15000 hours / 100000 cycles? I don't think so.

    The purchase price of the LED bulb is less than that of a traditional bulb; last time I bought a 150w Photocrescenta bulb I paid 15 euro, i.e. 3x as much.
    The energy consumption is 10w for the LED buld versus 150w for the Photocrescenta bulb. The life of the Photocrescenta is much shorter, typically 100 hours i.e. 150 times shorter! All in all the environmental footprint cradle to cradle of a LEB bulb is much, much less than a traditional bulb.
     
  23. mgb74

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    I suspect there are significant differences in the electronics of various LED bulbs. Better brands (like Osram) might have better performance that some of the cheap bulbs I see.
     
  24. ~andi

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    About the prices of the Photocrescentas, that's true. Because they're not made by Philips anymore and people overcharge. Many don't know those lamps are still manufactured by other companies. And then there's the shortneck/long-neck fairy tale that makes people believe those short-neck bulbs aren't available anymore and rare. If you buy them new, recently manufactured (e.g. Dr. Fischer is a manufacturer in Europe), you pay about 5 Euros per bulb. Depending on how much you buy.

    About the lifetime/cycles figures. Are they independently determined? Or in combination? Does it switch on/off for 100000 cycles and still make 15000hrs and vice versa.

    The instant-on thing comparable to tungsten is, afaik, only possible with a sort of standby circuit which requires constant power. I've read a paper on this a long time ago, I'd have too look it up what exactly it was.

    "The energy consumption is 10w for the LED buld versus 150w for the Photocrescenta bulb."

    That's true. But given the short period they're on, is this something that really matters? I'm more interested in the on/off cycles and the photo-relevant properties, instant on, stability of light etc.

    "All in all the environmental footprint cradle to cradle of a LEB bulb is much, much less than a traditional bulb."

    You seem to be very certain of this. I'm curious, how do you come to this conclusion?
     
    Last edited: Jul 10, 2017
  25. trondareo

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    I am looking for a lightbulb for a Durst Laborator 1000. According to the manual it is supposed to be about 3-4 inch or 80-90mm diameter opal. Has anyone found a suitable LED?
    (better to bump up this thread than start a new one)
     
  26. Hilo

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    Have a look at the posts in the Apug thread below. The opal bulbs I use with my L1000 have a larger diameter than what you say and in this thread I give the specs. These bulbs provide correct illumination. I have enough of these bulbs, but I am also interested in the led solution, if only for the 'no heat' reason. Ron (the OP) is a friend and I will ask him to help me test the better led bulbs in my L1000. This will take a couple of weeks for sure and probably longer, I don't visit here regularly - you are welcome to get in touch with a pm in case you have not solved this before that.

    https://www.photrio.com/forum/index...-138-enlarger-lamps-news.129970/#post-1714970

    Michael
     
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