It sounds sound in my mind.
I have a spare dichro head that I want to modify for using on an 8x10 enlarger.
My thoughts are that I should be able to just build a larger mixing chamber for the light source and make a larger diffuser and should be able to use that.
I beleive that this should work no problem, just decreasing the light intensity so I just need to compensate with a longer exposure?
What are your thoughts on this?
Add 3 more bulbs while you are at itYou idea is sound but the resulting light source will be on the dim side.
I thought of doing this with a Super Chromega Dichroic II color head. There would have been plenty of illumination with an 8X10 mixing chamber, even if it lost two stops.
I have had to find a lower wattage/ dimmer light source just because the "original" output was simply too high to my needs. I bet many people have the very same problem.
The main issues are light spotted areas and vignetting. If you can made a mixing chamber without this problems, I think it should work. But, if I were you, I`d not waste a minute trying to use a "hot type" bulb... if you`re decided to build something, I`d advice you to use a cold LED source even with under-the-lens filtering. I`m currently using a "prototype", and I`m pleased. Never ever hot bulbs&lamps again.
Doing some tests, it is definately going to be dim. So I have been thinking of getting some 250W quartz halogens. Have to rig them so they all go through the same set of filters, then through the infrared filter, into a new mixing chamber. Going to be an oven somewhere along the way so a couple cooling fans at least will be required.
I would love to go with LEDs but I figured the output isn't going to be bright enough, and also worried about the color temperature of the light. Need to have enough room for filtration....
I think LEDs are so easy, simple and cheap with condenser or flat diffuser heads. If you plan to use your enlarger with a color mixing chamber or with a blue-green source, things turn way much complex, and/or extremely expensive.
Don`t know which quartz halogens you mention, if they are the ordinary "stick" shaped ones I have, I think it`s not a good idea. Better to go with ordinary bulbs.
If you plan to rig a set of bulbs, use LED. There are quality LED bulbs in "classic" shapes, equipped with E27 (and E14) threads, made with a diffuser glass dome over it (something between frosted and opal); I have seen them in 2700 and 3000ēK (amongst many others), they are quite stable, no warm up is needed, and they are durable.
The output power is close to the usual 50 watt tungstens (most powerful ones), and the heat emission is almost negligible for a normal enlarger use (no need of cooling). Worth a try, definitely.
The LEDs work really well. I found this thread on APUG and modified my Omega E head to use the LEDs. Worked really well but requires under the lens filters (since I can't find 5x7 sized filters). Prints about grade 2 with no filters, and has the full range of contrasts available as if using an incandescent bulb. I've stopped using it since I found the Omega E to be a bit limiting in size and replaced it with a floor standing Durst. I plan on moving the head over to the Durst however.
I went with the 6500K LEDs and they are very bright. At least twice as bright as the original cold light, even with my kludgy mask in the middle to even out the output. Getting the light even across the whole frame is the hardest part.
You might be able to replace your halogen bulb in the Omega head with LEDs. Then you could make use of the filters. I don't know if you easily pack them in there with the required head sink, but it could be a fun experiment.
Well, I suppose it's easy enough to CC filter the light before it hits the dichro filters and mixing chamber.
What type of LEDs are everyone using? What type of wattage is recommended? Omega uses 250W of Halogen for 4x5, 1000W of Halogen for 8x10. Obviously the LEDs use a different rating for lighting.....
Is there any standard rating crossover that would ensure enough power?
Same experience here with ND filters; I have reduced the output from my Beseler 23 from 75 watts to 35 (equivalent)... it means around 4-5 watts in LED power. My usual enlarging times are around 10-15 seconds @ f8, which I consider just perfect.
Wayne, I`d opt for "domed" ordinary LED bulbs. A line of "naked" LEDs project multiple spots that need to be diffused prior to reach the film, so there is a need of a mixing chamber and a very high output. Also, a more or less complex circuitry is needed. My idea is to simply build a rack of bulb holders in the same way Ansel Adams did for his horizontal enlarger. It could be not so elegant, but probably the easiest and more practical way to do the work. With maybe nine, 6 watt bulbs (equivalent to 450 watts of light power), I think you could be served. You have to build the box, maybe you can buy one of those made for electronic devices, and simply attach the bulb holders&wires...
Larry, you could you provide us the link to Apug? It `d be great to read that thread. Thanks.
Just factoring in more/less wattage is the minor issue. Getting even diffusion is the real problem. Good
ole Ansel's idea was pretty hokey to begin with. An engineer he was not. You'd be better off seeing if
you could scrounge a workable used cold light. But none of the above ideas is of much use if you're
contemplating color enlargement. I assume you're not. A single intense halogen will work if you know
how to "tower" stage it thru multiple diffusers, but then heat & cooling becomes an issue. Check with
someone like Glennview and see if he has anything ready to go. He's an experienced jerryrigger.
Posting Permissions
Reply With Quote
Bookmarks