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bicycle LED as safelight
I know that this has been asked here before, but google doesn't supply
a suitable answer. Everybody seemed to want to talk about lowering the voltages on bulbs, not using LEDs. I have a pair of red LED bicycle taillights; three red LEDs each, red lenses, and intend to use them as safelights. I use variable-contrast papers. These are LEDs, not bulbs, so I figure they're more or less monochromatic. And I've used VC papers in red-bulbed safelight darkrooms before. Will this work? Seeing as there are commercially-availble LED safelighting solutions, it would be kind of silly for me to buy them specially, if I have something suitable already at hand. -Luigi www.livejournal.com/users/ouij Photos, Rants, Raves |
#2
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bicycle LED as safelight
Can I use a darkroom safe light as my bicycle led?
Never mind, I'll ask in the alt.mountain-bike NG. :-) |
#3
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bicycle LED as safelight
Luigi de Guzman wrote in message
I have a pair of red LED bicycle taillights; three red LEDs each, red lenses, and intend to use them as safelights. I use variable-contrast papers. These are LEDs, not bulbs, so I figure they're more or less monochromatic. And I've used VC papers in red-bulbed safelight darkrooms before. Seeing as there are commercially-availble LED safelighting solutions, it would be kind of silly for me to buy them specially, if I have something suitable already at hand. -Luigi LEDs definitely make useful safelights, and you don't need to shell out the big bucks for commercial LED safelights. But you need to know something about LEDs and their effect on photo paper, and you will need to do a little work. And most important, you will need to do a safelight test just as you would for any safelight. LEDs use various elements in their composition to get different colors, Unlike Laser Diodes, which put out light at just one wavelength, LEDs put out a band of wavelengths centered at a particular value. For example, a RED LED may put out light with the engergy centered at 630 nm and 99% of the energy between 615 and 645 nm. The problem is that this information is available for individual LEDs, but isn't usually provided by the people who assemble them into lamps or products. In general, photo paper is pretty insensitive to light with a wavelength longer than about 600 nano meters. That wavelength looks yellow-orange to the human eye. This says that a yellow LED will fog paper pretty easily (believe me, it does), an orange (amber) LED may fog it it the light is very bright, and a red LED can be pretty bright without fogging film. Filters can be used to help eliminate light with shorter wavelengths from the spectrum -- making the orange LEDs a little safer. A Rosco #24 Scarlet or #25 Red filter gel works great. It might sound like a RED LED is the way to go. Well... hold on. The other factor to consider is that the human eye is pretty insensitive to red. It sees amber much better. IMHO the best color to use is orange. If it is used with a red-orange filter, it can be pretty bright and not fog film. Where to get them... Among the most widely available and cheapest bright LED packages are truck tail lights. Check out the bus or truck in front of you next time you are out driving. These run on 12 volts and can be very bright. To power them, a cheap 12 volt power supply from Radio Shack should do the job. A rule of thumb is that you need 1 amp of capacity for every 25 LEDs. Here's another trick. I have a good general safelight, but some areas of the darkroom remain, well, dark. So I use little lamps with a single LED to light specific things. For example, I have a single LED that shines on the thermometer at the developing tray. I have another that illuminates the f stop scale on the enlarging lens. Yet another shines on the knobs on the radio. Shine is probably an over-statement. These run on almost no power and I have them set so they give me just enough light. That minimizes the possibility of safelight fog. Here are some useful web links... Vendors of LED tail lights... http://cgi.ebay.com/ebaymotors/ws/eB...m=2462175 543 http://www.superbrightleds.com/truck_lights.htm Web site with lots of LED info... http://www.ledmuseum.org/ Major makers of LEDs include Lumileds, Kingsbright, and Luxeon |
#4
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bicycle LED as safelight
Good one!
I think both of you should go test and post your results. "f/256" Can I use a darkroom safe light as my bicycle led? Never mind, I'll ask in the alt.mountain-bike NG. |
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