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  1. #21
    Ken Nadvornick's Avatar
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    Quote Originally Posted by polyglot View Post
    I did some safelight testing tonight with Arista paper and the 1.8W red LED that arrived first from eBay. It's OK at 16s but fails at only 32s of exposure.

    I tested again with two layers of rubylith over the front of the lamp and it passes at 512s (about 8:30) with pre-flashed paper. I didn't bother testing any longer than that because a) I'm impatient and b) I never have paper out that long.
    This has been my similar experience with my (635nm) red LEDs in the past. I know you know that, but thought I'd chime in as I've been following this thread.

    As mentioned several times earlier, using unfiltered LED light my pre-flashed tests failed after only a few minutes. But using a single layer of Rubylith I was able to completely eliminate the visually detectable blue and green spikes from my LEDs, then successfully test them with pre-flashed Ilford MGIV FB and RC as safe out to at least 60 minutes. I too gave up at that point.

    They are not as bright as you describe. But I use six of them mounted in-line on a DIY fixture held magnetically on the top of my suspended Thomas Duplex and bounced off the above white ceiling tiles. This gives an excellent spread of soft red that does allow fine easel focusing of projected images, while allowing easy visibility of everything else in the darkroom.

    And best of all, my whites stay brilliantly white. Even when using Slavich papers.

    This is a valuable thread.

    Ken
    "Hate is an adolescent term used to stop discussion with people you disagree with. You can do better than that."
    —'blanksy', December 13, 2013

  2. #22
    L Gebhardt's Avatar
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    Quote Originally Posted by polyglot View Post
    I did some safelight testing tonight with Arista paper and the 1.8W red LED that arrived first from eBay. It's OK at 16s but fails at only 32s of exposure.

    I tested again with two layers of rubylith over the front of the lamp and it passes at 512s (about 8:30) with pre-flashed paper. I didn't bother testing any longer than that because a) I'm impatient and b) I never have paper out that long.

    The thing is so bright that it's impossible to compose in the easel with it on, because it completely washes out the projected image. Really, incredibly bright, with perfect visibility into the darkest corners of the darkroom; probably a good 6 stops brighter than the 3-LED bike light I was using. I'm going to have to rig up a switch or something, maybe some black tape across the front to dim it by a stop or two.
    I didn't even bother to test mine without the rubylith, however I'm surprised it's so short of a time.

    I really appreciate the fact that my timer turns off the safelights now that I have the red ones near the enlarger. Can you use a different relay to switch the power? The one I'm using has three wire positions, so when you close the enlarger wire it opens the safelight wire. These are very small and cheap from ebay and amazon.

  3. #23
    polyglot's Avatar
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    My timer is the home-made one in my signature. I am seriously considering pulling out the triac that it currently uses and swapping in a double-throw mechanical relay to switch the power between safelight and enlarger outputs.

  4. #24
    Paul Glover's Avatar
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    http://dx.com/p/18-led-e27-light-bulb-110v-red-5136 Tested safe out to 8 minutes using something akin to the Ilford test on Adorama VC RC paper. Just one light bounced off ceiling with the paper directly beneath.

  5. #25
    David Brown's Avatar
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    I have had a failure of an led used as a safelight. See post #5 in this thread.

    Short background: I started a thread in January about led lights and relays. (see http://www.apug.org/forums/forum43/1...mers-heat.html ) I was considering changing out the tungsten white lights in my darkroom with leds and was asking about heat. That issue has been resolved, however, I have to admit I have never gotten around to changing the tungsten bulbs. In any event, the discussion turned to leds and relays (also resolved) and then to another thread in June (see http://www.apug.org/forums/forum43/1...9-99-safe.html ) to using leds for safelights.

    The result of all this is that I ordered and installed and tested two of the leds mentioned in the original post of the June thread. (see entries #8, and then #20, where I eat a small bit of crow)

    I am disappointed to report that one of the leds has failed. I do not know why, and I realize that one is not a sample. I have ordered two more since the price of two bulbs and shipping is just over $10. I will replace the failed one and have the other as a spare.

    I hope that I just got a bad unit, but would be interested in any other (albeit anecdotal) experiences with any failures in led lights.

    I did have the safelights switched through the enlarger timer. The prior discussion was concerned with the led possibly damaging the timer and not the other way around. I had inadvertently left the timer and safelights on for a couple of days (normally turn everything off when not using the darkroom, but I wouldn’t think that’s the cause. However, almost immediately after doing so, the bad bulb first went dim, and then out completely.

    I’ve got a lot of printing to do in the near future, so the replacement bulb will get a good workout. We’ll see.
    David
    Taking pictures is easy. Making photographs is hard.

    http://www.behance.net/silverdarkroom
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  6. #26
    polyglot's Avatar
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    LED elements themselves are pretty rugged, and should not fail until about 50k+ hours of normal use. The exception is if the diode has insufficient heatsinking and is allowed to reach high (100C) temperatures. Usual behaviour is to drop to half brightness after about 60k hours and decline exponentially after that (e.g. quarter brightness at 120k hours). A cheap bulb with insufficient heatsinking will dim noticeably in much less time.

    More likely is that the switching regulator built into the bulb failed. High quality regulators are quite expensive, it's the reason you can get generic $5 LED bulbs from China but a good Philips unit is still many tens of $.

  7. #27
    RalphLambrecht's Avatar
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    this is an interesting subject, I tested quite a few LEDs, and in my experience, it doesn't seem to matter how well the wavelength seems to fit the paper; as long as the light is bright enough, it WILL FOG THE PAPER. the only way to protect the paper is to dim the light.(H=E*t)You have to bring E down to maximize t.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  8. #28
    NedL's Avatar
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    I also ordered 2 of the bulbs mentioned in the original June thread, for around $10 including shipping. One is still in the box an the other has been used continually since then. It's up pretty high and aimed at the ceiling, and that's how I tested it with my papers. The light is pretty weak, just enough for me to see what I'm doing... My "problem" paper was Arista.edu VC paper, and since changing to this bulb all is well. I think reported on my tests in that thread, but since then I've also been using Ilford MGWT with success. The bulbs are small and I almost took one on vacation over the summer to use for changing paper negatives away from home.... ended up not doing it but they are small enough to make that a nice option.

  9. #29
    David Brown's Avatar
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    Quote Originally Posted by polyglot View Post
    More likely is that the switching regulator built into the bulb failed. High quality regulators are quite expensive, it's the reason you can get generic $5 LED bulbs from China but a good Philips unit is still many tens of $.
    Yep. These are $3. Others have had good luck with them and I probably got a bad unit. I ordered two more, as I said. However, if one of them fails in a few months, I won't order any more. I have enough standard safelight fixtures and spare filters to last me probably as long as I'm going to want to do this.
    David
    Taking pictures is easy. Making photographs is hard.

    http://www.behance.net/silverdarkroom
    http://silverdarkroom.wordpress.com

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