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.in...-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/forum43/9...eds-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.