Survey of paper-safe red LEDs (safelights)
I've been using a 3-LED bike tail light for my safelight; it's enough illumination (just) and quite paper-safe. I wanted to buy a mains-powered LED bulb to get better illumination and not change batteries, so bought a couple to try. I've been testing spectrum by diffraction off a CD and my $3 bike light shows only red, maybe orange, components.
The first lamp I bought is a 1.8W, 38-LED, 220-240V E27 thing from China for $1. The branding on the box is "FLY" and three balloons; it's made by Shenlong Company Ltd. Currently listed on eBay as #290687055751.
The CD test shows it has significant spectrum into green and even blue so I haven't paper-tested it.
I'll post more as I receive more in the post; can other people please post their positive and/or negative experiences with specific LED bulbs? There are a few that have been reported as good in a bunch of other threads so I'd like to gather them here and make this a sticky. Please tell us whether you did the CD test and if you've checked for paper-safety, which paper(s) and durations and whether you did the test properly with pre-fogging.
I've been using a head lamp with a single red LED for years. No problems.
I should have thought to try ebay for LED bulbs. I've got a couple of these in use, but they were pricey relative to what you paid. They also show a bit of yellow/orange and green when looked at with a CD. So I wrapped them in rubylith and they work very well. I have tested them with paper out to 10 minutes from just a foot away when used this way and they showed no problem. I did not test them without the RubyLith. They are very bright.
I don't think any of the red LEDs are only going to be a pure red, so you may want to get a few big sheets of rubylith. The same LED viewed through rubylith shows only a red spectrum. I just taped the rubylith to the bulb with clear packing tape; not pretty, but effective.
What are the benefits of using LEDs over a regular old Safelight like an Ilford 902?
As discussed in this thread: http://www.apug.org/forums/forum43/1...9-99-safe.html
The LED in question is this one: http://www.superbrightleds.com/morei...60-degree/440/ It may or may not be suitable for your use in Australia, however.
Anyway, I bought two of these as a result of this tread and tested them, and reported this in the above thread:
"... I re-tested my current setup with multiple 0C filters that had tested "safe" before, and it tested safe again. I then used the same procedure using the pair of new LED bulbs, and they, too tested safe.
"(I probably should have tested just one LED bulb first, but I reasoned that if the pair passed, I wouldn't need to test just one by itself. Turned out to be true.)
"I then combined the new LEDs with my current safelights and tested that, and also got a "safe" test. I was both surprised and pleased. I finally extended the test from 7 minutes (using the Kodak procedure) to 10 minutes and still got a clean, safe test!
"I use the Kodak method http://www.kodak.com/global/en/consu...Safelite.shtml. This is very similar to the Ilford procedure http://www.ilfordphoto.com/aboutus/page.asp?n=148.
"The Kodak test goes to 7 minutes. It was a simple step to add another 3 minute exposure to get a cumulative 10 minutes of safelight exposure. All of this was done with Ilford Multigrade paper.
"Disclaimers: Different papers must be tested for, and each darkroom setup, or change thereto, must be tested.
"Therefore, all this proves is that the specific LEDs mentioned by the OP work in my darkroom with Multigrade. It does not speak to all red LEDs, other types of red bulbs, strings of Christmas tree lights, etc."
Bottom line: (IMHO) none. But see: http://www.apug.org/forums/forum43/1...safelight.html
Originally Posted by Ghostman
I am not against LEDs. I believe LEDs will replace tungsten in the future. But there is certainly nothing wrong with using either light source with a proper AND TESTED filter.
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rbeech: do you have a model number or link?
Larry: I will probably test again with rubylith as I have a bunch of it. It'd be nice though if we could find a handful of widely-available known-good models that don't need additional filtering.
I also just tested some individual bright-red LEDs; very monochromatic and safe at around 650nm. They're not a readily-usable bulb module though.
Ghostman: if the LED spectrum is paper-safe, it will remain so. There is no filter that can fade or scratch and therefore become unsafe. The idea is that bandgaps in the LEDs are finite and therefore the right LEDs should be monochromatic with lower photon energies than the activation energy of the paper emulsion. The right LEDs are inherently safe for basically infinite exposure time, whereas a filtered incandescent will always eventually fog paper, even if it takes an hour or two because the filtering is not capable of cutting out 100% of the green/blue/UV output from a filament.
David: what is the voltage rating on those? I don't see anything on the webpage; is there something marked on the bulb or its packaging?
Interesting. Many thanks. I'll investigate this.
Originally Posted by polyglot
Originally Posted by polyglot
Last edited by David Brown; 07-15-2013 at 02:21 PM. Click to view previous post history.
I use a red OPTILED Festival lamp. It's got a narrow spectrum, standard Edison screw base, 35,000 hour rated life and is universal voltage. Specifications here:
I've used it with a variety of papers, including very sensitive VC types, and experienced no fogging out through six minutes exposures. Price, considering it can be simply screwed into a standard lamp socket and that one will probably last the rest of my life, seems very reasonable to me:
I bought a half dozen with the intention of placing them uniformly along a planned long, narrow, permanent darkroom in a home to be built. For now, a single one bounced off the ceiling is adequately bright in my small, temporarily converted bathroom occasional darkroom.
I installed this one: http://dx.com/p/e27-0-7w-7-led-25-lu...-265v-ac-37160 in the community darkroom that we run here and a member of the group said that she tested it and it seemd safe.
I need to do some tests myself in order to be able to recommend it without any doubts, though, because I am not sure if she did a thorough test !!
I have a couple of good darkroom safelights in my own space (Osram Duka, Ilford) but I don't know if I will be able to find a replacement for the tungsten lamps found inside once they're gone !!