DIY 4x5 enlarger and LED head

[konakoa]

Hello folks,

I'd like to share a substantial update I've made to my modified enlarger project. This project is converting a small medium format enlarger (a Beseler 23C) into a large format enlarger, and building a light source for it.

I've rebuilt a new enlarger, and I have a new version of the LED head. It can be seen at:

http://www.deadbread.com/crumbs/23c.html

I've been working on this for many months. I'd love to hear your comments!

(Hey, cool! This is exactly my 100th posting here.)

 

[anikin]

Really cool! Thank you for taking the time to set the page up. It is super informative! I'm thinking about modifying my enlarger in a similar way. I already ordered couple 3W RGB LEDs and was planning to use one or two of them in mixing chamber of my dichroic enlarger. It's so good to know that UV LEDs are not necessary, I was really worried about that. From your experience, do you think
3W LED would be enough for 6x7 enlarger, or should I get something more powerful?

Thanks, Eugene.

 

[Mainecoonmaniac]

Oh oh..the gears in my head are turning. Am I going to get rid of my 45mx dichroic color head? Does the annoying cooling fan justify changing over to LED technology? Great website link!

 

[coriana6jp]

Thank you for sharing this. I think I have a new project for my holiday vacation.

Gary

 

[pcyco]

hallo

t h a n k s

thomas

 

[amac212]

This is partially over my head (particularly the bit about the power connections that you had to finagle), but I am utterly wowed and impressed! Thank you for sharing this!

 

[ic-racer]

Fantastic work!

From the looks of it, the blue LED puts out too much green. The UV LED puts out no green, that it why it works better.

You could cut up a #5 filter and put the little pices over each blue LED. It should not make it much slower, because you would only be blocking the unwanted extra green coming through.

Certainly fertile ground experimentation.

 

[Steve Smith]

I found something odd with my LED head. The first print I made was with both green and blue LEDs on and as expected (hoped) the print was of medium contrast. The next print I made was with just the blue LEDs. That too was as expected - higher contrast, possibly grade 3.5

The strange thing was that both exposures were for the same time.


Steve.

 

[ic-racer]

You did not mention it, but I think you discovered that the farther the diffuser is from the LEDS the more of a hot spot you get in the middle. So you are making the LED grid bigger than 4x5" right?

 

[mjs]

Great article, very clear, informative and helpful. Thanks!

Pinky! To the lab...

Mike

 

[konakoa]

Eugene, see if the manufacturer gives the range of color wavelengths for the 3 watt RGB LED. The small blue LEDs I used (at 470nm) weren't, well, blue enough. The RGB LEDs I used also didn't go far enough into the spectrum to work well.

Sounds pretty neat refitting a old color enlarger. You'll lose a lot of light intensity bouncing around in a dichroic mixing box--this is a complete guess, but I'd say you'll need several of the big RGB LEDs in the mixing chamber to match the original halogen bulb.

ic-racer, yes, I deliberately made the grid bigger than the 4x5 frame as I knew the corners wouldn't be as bright as the middle. The grid I built is six inches square illuminated, and it's cropped in slightly from that by the bottom portion of the box/housing that holds it all.

 

[heespharm]

i just use an old crown graphic, a graflarger and a copy stand... pretty much the same concept with less diy

 

[1banjo]

Hey konakoa
I like the LED thing !
but Beseler made a 45H it was about the same frame as a 23C II XL
but it has a 4x5 Condenser Head !
I have one & then made one with a Cold head
1banjo

 

[cmo]

Building an LED enlarger head is an interesting project. My enlarger, an Agfa Varioscope 60, is a great machine like a Focomat II, but it was was a bargain because it has a condensor head and no filter drawer. This series is high on the list of very good enlargers that could become the best choice for variable contrast papers.

Below the line, how much would it cost to build such a head? How much time is needed to build it?

I also saw this project:

http://www.huwswebthing.talktalk.net/leden.htm

Combining an LED head with an analyer/lightmeter timer is a logical step towards a homemade Heiland Splitgrade...

 

[anikin]

Thank you konakoa for encouragement!

An update - I finally received the 3W RGB leds. By running two of them into the mixing chamber of Beseler 67s I get about 1.5 stop less light than the halogen. Not perfect, but it should be usable for initial testing. I'm now in the process of building an f-timer with R/G/B controls...

 

[alanrockwood]

Very nice work. I have been wondering how one might do this sort of project.

One (of many) things that have slowed me down from considering doing a similar project (i.e. LED conversion) is that data there is no data on how contrast grade varies with wavelength. This would require a lot of experimentation to unravel, as you are finding out.

 

[Steve Smith]

One (of many) things that have slowed me down from considering doing a similar project (i.e. LED conversion) is that data there is no data on how contrast grade varies with wavelength. This would require a lot of experimentation to unravel, as you are finding out.

I have decided that I don't need to know what grade someone has assigned to a particular contrast response. I just need to know that I can increase or decrease it.


Steve.

 

[alanrockwood]

I have decided that I don't need to know what grade someone has assigned to a particular contrast response. I just need to know that I can increase or decrease it.


Steve.

However, it would be nice to know which wavelengths produce maximum contrast, which produce minimum contrast, and which wavelengths produce little or no paper response. This information would help in choosing which LEDs to use for designing the LED array.

 

[ic-racer]

Yes, getting a single test-LED to evenly illuminate a 21-step wedge may not be so easy.

 

[konakoa]

From the looks of it, the blue LED puts out too much green. The UV LED puts out no green, that it why it works better.

I've been curious about what you had said, so I went about trying to find out. What I did was build a home-made spectroscope and I sampled several light sources. I went a bit more in depth here: www.deadbread.com/crumbs/spectro.html You were spot-on Ic-racer, there was some green hidden inside the blue LED spectrum. No green in the ultraviolet LEDs; yet there was bit of blue.

 

[symmar_man]

I've been curious about what you had said, so I went about trying to find out. What I did was build a home-made spectroscope and I sampled several light sources. I went a bit more in depth here: www.deadbread.com/crumbs/spectro.html You were spot-on Ic-racer, there was some green hidden inside the blue LED spectrum. No green in the ultraviolet LEDs; yet there was bit of blue.

Great measurements! What I would like to see is the spectrum of the blue and green grids of the Aristo 4500 and the Zone VI 8x10 VC heads.