It seems like they are being used in everything, and I believe they have been used in enlargers before.
How expensive are they. How difficult to control are they.
What would be the difficulties in putting a couple different colored ones in a lamphouse and using them for enlarging
They're a fairly weak light source, and would be worse than miserable for any kind
of color printing. Maybe not such a great idea for VC papers either, which are
dependant upon colored light.
I've converted to red led safelights in my darkroom; got some screw-in led bulbs that make clean red light for a couple bucks each from dealextreme. Put them on a tracklight and pointed the cans where I needed for nice illumination. The cutoff is nice and I can make it far brighter than I thought possible without fogging paper. So bright, I sometimes turn them off while focusing a negative for better visibility.
For an enlarger, some people have done work with this and it interests me a great deal, but it's not as simple as swapping a light. The VC papers have spectrum analysis curves showing which colors their high contrast component is sensitive to and which part of the spectrum their low contrast part is sensitive too. That's easy to produce using an incandescent bulb, as they produce light nicely in all spectrums and you can just use a filter or dichroic glass to get the color components you want. LEDs don't transmit in all parts of the spectrum, which made them great for my safelight. Different colored LEDs have different outputs in different color bands and they don't neatly line up with what VC paper needs. Theoretically white is white, but there are as many colors of white LEDs as there are shades of white paint on the market. LEDs make white by combining colors so it's a bunch of color bands put together that don't make a perfect uniform output of spectrum. The people that have done this (search the forum archives here or at apug), have done special testing to show exactly what sort of contrast they can get. Looks like they've got the basics down, but can't yet beat normal light for the rare ends-of-the-scale contrasts, which we hope not to make negatives that need that anyways.
I'm thinking of sometime after I get a few other projects wrapped up, getting one of those LED panel lights used for video fill light and using it for a custom enlarger head. Perhaps build an 8x10 enlarger with it and use MG filters for provide the contrast. My main interest in this is to have a LF enlarger that doesn't need a noisy blower motor on the wall to keep it cool. If an LED enlarger needed cooling, probably a quiet little 80mm computer case fan would work fine.
compared to what?Originally Posted by Drew Wiley
compared to a cold light head, the proper led's with some diffusion will provide more output at the distances used for enlarging.
The led's we use for the motion picture industry (3200k and 5600k)have very high output for their size and power consumption and I believe the output would be suitable for VC papers with standard filtration.
Jp, a 1x1 tungsten light panel would be ideal but they are $$$$$$.
There's another product (not as high output) called Lite Ribbon that comes in 16.5ft rolls and runs off 12v dc. It's also $$$$$ but there are generic rolls on ebay for much less. It's fun to play with but not sure it would give a bright enough/clean enough output.
I was thinking along the lines of ebay items 310177861085 or 400196753412 for a powerful but efficient LF enlarger light source.
LEDs are now being used for lighting for film production so the output can be pretty high. I read an article not too long ago about someone making a head for a 4x5 enlarger with some. They come in little strips you can wire together to make the size source you need. google 'led enlarger head' there are quite a few hits.
Most of the obstacles involved with making an enlarger head with LEDS have been overcome by individuals that have posted their success stories in various blogs and forums. However with the glut of dichroic heads on the market, it seems like a lot of work.
Well, I don't know a damn thing about electronics, but I do see that tvs now use LEDs and it seems to me they are pretty bright and have all kinds of colors. I would envision a Multicontrast Black and white light source as a minature TV with the required blue and green light.
Five or six years ago, I did some work using blue and green LEDs for VC enlarger head. Ilford paper has a high (blue) contrast sensitivity of 420 – 470 nm. , and a low (green) contrast of 520-530 nm. Unfortunately the LEDs available at that time had a bell shape wavelength curve. The green LED wavelength crossed into the high (blue) contrast range . The blue LED had a cleaner cut off and did not affect the low (green) contrast as severe. Maybe a cut off filter to block the lower frequencies emitted by the green LED would do the trick,,,,,,,,,,,,
Bill Kumpf
LEDs are the future of lighting. I'm using a homemade head on my Bessie and it works great. Take a look at my notes here: http://www.rwhawkins.com/wordpress/archives/99
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