led Lights for enlarger

[gary892]

I am thinking about designing a led light system for my Beseler 4x5 enlarger.
I seem to recall some discussion about a specific color, possibly in the blue wavelength, for the led lights.

I did a quick search on the site and nothing was returned in the results.

Anyone have thoughts on best practices for building this?


Thanks

Gary

[C. D. Keth]

I would do some research and see what the main wavelengths are for exposing the two layers of variable contrast paper. That should give you the two colors you want to be mixing. If you put each color on a dimming circuit, you'll be able to make settings that correspond to each filter grade.

[bigdog]

http://www.largeformatphotography.info/forum/showthread.php?92971-Possible-LED-light-source-for-enlargers

[chassis]

Gary, if you work out something that works, would you be willing to post a how-to or "recipe" for it? I have a Beseler 4x5 also, and would like to convert to LED.

[Bob Farr]

www.kienzle-phototecnik.de

They have an led light source, I was very tempted to get the VC light source. Discouraged by the price.

Cheers,
Bob

[ataim]

As a matter of fact I pursued this over the weekend. I searched a while back and found out that Ilford VC paper is sensitive to blue and green light. Blue having a range of 450-460nm and green having a range of 525-530nm. After searching Google finding the required LED is pretty easy, but a PCB has a little harder to source. In my searching I stumbled across stage LED lights that have Red Green and Blue LED lights. So I figured what the heck and purchased a Chauvet Thin-Par 56 led light and an Obey 3 DMX controller (less than $100) and gave it a try (both returnable).
First, when using my timer I did not find a way that would allow an instant on (if you just plugged the light in it would first flash white light, then delay a few seconds before coming on and then program it for use with the DBX Contoller) or when the DBX controller is powered on it would not go into manual mode first, it would power up in program mode. Second, the wave length for the blue was not correct it printed like about a 4 filter would. Third, the green was not correct either, printed like a 1 filter would. The beam angle of the LED was 23 degrees which required the light to be placed about 8” above the enlarger to insure equal coverage without any “hot spots”. I used an old foldgers can lined with silver tape to raise it up. The Par 56 is the correct size, and the light was somewhat brighter than my Zone VI cold head. I'm returning the light and controller, but I am still looking at buying the raw LED, PCB and trying again with the correct LED wavelengths, but it will be a few weeks before I can.

[Jerry Bodine]

Have a look at this conversion of a 5x7 Omega.
http://www.apug.org/forums/forum43/96720-converting-omega-5x7-e3-cold-light-head-leds-100-a.html

[chassis]

Paul, very cool. I am interested to learn how your experiment progresses. My interest is in an LED variable contrast light source that eliminates the need to use VC filters in the drawer. Does your system allow for this, or would it in its ultimate embodiment? Thanks for posting the photos and comments.

[gleaf]

Cree makes a different series that has a blue and a green options. Due to the power output differences it would take a 3:1 count ratio in diodes to gain the same lux but contrast control can then be controlling the diode string current relative blue and green. 300 ma is easy for a 1 amp rated LM317 three pole regulator rigged for constant current. Control the current controls the led output power. Would behave much like the Zone VI cold light head. If you used the white for focus you would have thebright white to focus, then no filters for multi-grade paper exposure.. 3 led per string and an old PC power supply for 12 vdc. Hmmm. Edmond optics has opal glass for a diffuser. Love the Folgers s can... Oh No another project...

[jp]

grades 1-4 would meet 99% of my needs. Keep a set of filters if you need the extremes. If the DMX controller allowed an external control to on/off the light, that could be used with a timer. I don't know the DMX product options though.

[cardiomac]

One of my Omega LED diffusion enlarger heads (Model 2 or Model 3) may work if you simply set it on top of the upper bellows of your Beseler enlarger. You would need to cut a piece of cardboard to keep light from leaking around the rectangular lamp housing as it sits on the circular opening. I can supply a lamp without the Omega-specific vertical arms if desired. You can send it back if it doesn't work.



www.modernenlargerlamps.com

[Leigh]

One of my Omega LED diffusion enlarger heads (Model 2 or Model 3) may work
www.modernenlargerlamps.com
What's the real URL? The modernenlargerlamps domain name just contains a redirect.

- Leigh

[cardiomac]

What's the real URL? The modernenlargerlamps domain name just contains a redirect.

- Leigh

The redirect is to www.modernenlargerlamps.com which is the real URL.

[Aldo]

This thread is also very important for me !
Led light is very different in spectral distribution than tungsten lamp, and has different problem: power (that means more $$$ ) and rear heat ...
I live in Italy and there are many Leds producers , i can ask technical data sheets ...

[ic-racer]

As a matter of fact I pursued this over the weekend. I searched a while back and found out that Ilford VC paper is sensitive to blue and green light. Blue having a range of 450-460nm and green having a range of 525-530nm. After searching Google finding the required LED is pretty easy, but a PCB has a little harder to source. In my searching I stumbled across stage LED lights that have Red Green and Blue LED lights. So I figured what the heck and purchased a Chauvet Thin-Par 56 led light and an Obey 3 DMX controller (less than $100) and gave it a try (both returnable).
First, when using my timer I did not find a way that would allow an instant on (if you just plugged the light in it would first flash white light, then delay a few seconds before coming on and then program it for use with the DBX Contoller) or when the DBX controller is powered on it would not go into manual mode first, it would power up in program mode. Second, the wave length for the blue was not correct it printed like about a 4 filter would. Third, the green was not correct either, printed like a 1 filter would. The beam angle of the LED was 23 degrees which required the light to be placed about 8” above the enlarger to insure equal coverage without any “hot spots”. I used an old foldgers can lined with silver tape to raise it up. The Par 56 is the correct size, and the light was somewhat brighter than my Zone VI cold head. I'm returning the light and controller, but I am still looking at buying the raw LED, PCB and trying again with the correct LED wavelengths, but it will be a few weeks before I can.

Looks like a good solution, I'm surprised it did not work.. #4 and #1 grades are pretty close. How did you test that? Also, did you try putting the timer between the power supply and the LEDS.

[ataim]

Looks like a good solution, I'm surprised it did not work.. #4 and #1 grades are pretty close. How did you test that? Also, did you try putting the timer between the power supply and the LEDS.


I tried different ways to run the lights. The only solution was to use the sliders on the DMX along with the metronome. As far as judging the grades, I simply printed full green and blue (one at a time), and then compaired to my Ilford MC filters of the same print. I split print 60% of the time and really like to burn in highlights with a 00 filter.