LEDs for enlarger light source.

[Martin Courtenay-Blake]

I know there was some discussion about using LEDs as a light source for enlarging some time ago. Just wondering if anyone is using such a source for monochrome printing, and, how they are getting on with it. I have a 5X4 enlarger (similar to a De Vere) with a digital closed loop colour system which is unfortunately no longer working. As I install a lot of LED lighting for a living I thought to rip out the guts of the head and replace with a suitable grid of white, blue and green Cree LEDs. It would be simple to set up a DMX controller for altering overall intensity and individual colour internsities to give grade control, or adjustment for different paper sensitivities.

Before commiting myself to the expense and work I would really like anyones views on the efficacy of LEDs. Any comments would be very gratefully received.

Martin

[AnselAdamsX]

I'm interested as well. I have some spare micro controllers and I just purchased a single green and blue luxeon LED's. I think I will try contact printing with the bare LED's to see how well they work. It's one of my back burner projects.

[DKirk]

I'm quite interested in this too, I recently held an open house exhibition in Fife, using 6w LED spots, and the ewwect was impressive. So LED technology has matured to a significant level for this, I just wonder how to try this out my self. I've made an incredibly simple 'UV Oven' for clearing the brown discolouration off Aero Ektars, so I'm curious about making a UV enlarger head (though the price of the specific UV leds at a sufficient out put is still rather steep.

[georgl]

A small German company from Wetzlar (I think the founder was an Ex-Leitz-engineer) called Heiland makes the so-called "Splitgrade-system" as an LED-version:

http://heilandelectronic.de/led_kaltlicht

It can be adapted to various enlargers, even 8x10" (the bigger, the more sense the LED-light-source makes). It's powerful, doesn't need active cooling and allow internal control of gradation and red-light without additional filters.
It consists of the LED-light (replacing the old head), a controlling device (replaces the clock) with a little probe which works as a light/contrast-meter. You program the paper (can be updated), measure the relevant areas of the negative while being enlarged and the controller calculates the EXACT exposure time and gradation - works incredibly well, I use it since nearly 8 years - although it's not a cheap solution (I have the older kind with an electric filter and a conventional light-source). I think they also corporate with Kienzle, the last high-end-enlarger-manufacturer I'm aware of - make sure your grandkids also get interested in Photography^^

[Sal Santamaura]

...Heiland makes the so-called "Splitgrade-system" as an LED-version...It can be adapted to various enlargers, even 8x10" (the bigger, the more sense the LED-light-source makes). It's powerful, doesn't need active cooling and allow internal control of gradation and red-light without additional filters....I have the older kind with an electric filter and a conventional light-source...Here's the English version of that page:


http://heilandelectronic.de/led_kaltlicht/lang:en

I had Herr Heiland adapt his 4x5 version of the LED source to my Beseler 23CIII four years ago. Challenges presented by the Beseler's configuration drove use of a larger than 6x9 source; it can be transferred to most 4x5 enlargers in the future if I ever wish to do so.

One of the design parameters you'll need to address is even illumination across the negative. Heiland does that by using a large number of small LEDs in combination with built-in graduated neutral density filtration. Although Internet research might turn up previous DIY projects which claim to have achieved even light by laying out fewer LEDs in some "unique" patterns, I'd be more confident in the Heiland approach.

[Steve Goldstein]

If you're really into do-it-yourself there was a very nice thread on APUG that you can find here:

http://www.apug.org/forums/forum43/84944-diy-4x5-enlarger-led-head.html

The deadbread.com domain seems to be defunct and I don't know where the pages have moved to, but you can probably PM the original poster. He did a lot of experimentation and found that using blue and green LEDs wasn't so good because the spectrum of the blue diodes actually extended into the green. The result was that he couldn't achieve higher contrasts. UV LEDs worked a lot better.

[Martin Courtenay-Blake]

It seems like there is an interest so I'll look a bit further. I think the problem for the guy on the APUG forum was using RGB LEDs. I find there is always overlap between the colours and they are very difficult to control accurately. It is now possible to get 3W single colour units from Cree and other manufacturers. The only drawback is they will need very substantial RGB dimmable drivers (with DMX512 control) to get enough output for a range of grades. I have used some pretty big ones in domestic lighting setups without resorting to mains voltage drivers as used for stage and screen.

I'll let you know how it all goes.

[Roger Cole]

I am. I bought a lamphouse from a fellow selling them here. I'm sure a little searching will turn it up or I can do it later. It replaces the incandescent one on my Omega DII. It works great. Speed is almost exactly between what I get with a 75W PH211 and a 150W PH212, results indistinguishable, no worries about heat and no need to stock bulbs, no changes with age over time either. (I do still have my stock of bulbs though, for the day I get back into color.)

He later offered a head that replaces the entire light source for diffusion but besides the additional money I didn't buy one because it requires under the lens filtering for VC filters. I still think about getting one, though.

[polyglot]

... no worries about heat and no need to stock bulbs, no changes with age over time either.

LEDs do actually fade with time, at a rate that depends on how hard you drive them. A poor quality LED being driven at its rated power will often be down to 50% brightness in about 2000 hours though a high-quality LED being driven lightly (about 60% power, which is often close to 90% brightness) can easily last 50-100k hours. It seems that the main issue is heating of the junction, causing the dopants to migrate. And some white LEDs (which are UV+phosphor) have lenses and phosphors that get damaged in the long term by the UV.

[Larry Gebhardt]

I built one that used white Cree LEDs based on this thread over on APUG: http://www.apug.org/forums/forum43/96720-converting-omega-5x7-e3-cold-light-head-leds-100-a.html. Worked really well for the few months I used it. I replaced the E3 with a Durst 138S, but I now have a plate to let me easily mount this head on the Durst. Unfortunately I need to find a source of 5x7 (really 6x8) contrast filters as my below the lens filters don't fit the new lens.

My eventual plan is to make a multigrade head with an Arduino as the controller / timer (based on Polyglot's fstop timer). I just need a ton more time.

[Steve Smith]

I have converted my DeVere 54 with the PCB from an LED stage light. No need for a DMX controller. Just a power supply and a set of switches.

I plan to change my light source soon though. The company I work for is working with this company: http://designledproducts.com/

I would like to use something of theirs in a suitable size.

My method, also on APUG:

http://www.apug.org/forums/forum43/62902-red-green-blue-led-head-stage-light-enlarger-light-source.html
http://www.apug.org/forums/forum43/79213-led-enlarger-head-update.html
http://www.apug.org/forums/forum43/79848-results-led-enlarger-light-source.html


Steve.

[jeroldharter]

...

I had Herr Heiland adapt his 4x5 version of the LED source to my Beseler 23CIII four years ago. Challenges presented by the Beseler's configuration drove use of a larger than 6x9 source; it can be transferred to most 4x5 enlargers in the future if I ever wish to do so.
...

Sal,

The documention seems a bit vague. Do you plug this into a regular timer? Does it require manual filtration above/below the lens? How do you like using it? You are the first person I have heard using one of these. I wonder how much the 8x10 version costs and how even the light would be.

[Roger Cole]

Here's the post where I responded and bought the one I have:

http://www.largeformatphotography.info/forum/showthread.php?85476-LED-Lamp-House-for-Omega-D-Series-Enlargers

I mentioned this was in progress at the time of my last post there, but Cemil replaced the original cord with a three prong grounded cord. It did indeed help the radio static issue, though there is still some.

[Sal Santamaura]

...The documention seems a bit vague. Do you plug this into a regular timer?...Heiland's LED source works with the Splitgrade controller instead of the filter module otherwise mated to an enlarger's standard light source. This page


http://heilandelectronic.de/splitgrade_filterautomatik

describes (at a high level) what the standard filter module-based system does. There's a probe attached to the controller that one uses to read a projected image on the easel. Based on the specific paper and probe readings, a print exposure is automatically determined. My experience is that this results in a good first work print requiring fewer refinements than an open-loop approach.


...Does it require manual filtration above/below the lens?...The LED source provides all contrast control via its array of different color LEDs, including blue and green exposures (automatically sequenced for times based on grade/exposure settings in the controller), white light for focusing/omposing as well as red.


...How do you like using it? You are the first person I have heard using one of these...Here's what I wrote when Juergen Heiland asked if I'd be willing to have something included in the "Customer Feedback" section of his Web site:


After four years of use, I am very pleased with the LED light source on my Beseler 23CIII. Due to that enlarger's configuration, the job involved a lot of custom adaptation, which Heiland executed in a most elegant manner. I've been contact-printing large format negatives almost exclusively, so the probe and evaluation functionality sit unused, but consistency and precision of exposure/contrast control as well as extremely even illumination are great benefits. The LED light source can make any work quicker, easier and more enjoyable -- I highly recommend it!



...I wonder how much the 8x10 version costs and how even the light would be.Four years ago when I decided to use my then-company's annual bonus payment to buy the Heiland source, currency exchange rates weren't quite so bad. Today, especially since I've been forced into retirement in the interim, it's unlikely I'd spend the not-inconsiderable amount Heiland charges for even a 4x5 adaptation. The dense LED array and graduated neutral-density center filtration make illumination perfectly even; scaling up to 8x10 ought not degrade that at all. The 8x10 price now is probably breathtakingly expensive. However, finding out would be straightforward. Juergan Heiland is fully capable in English and responds rapidly to email questions. He can be reached at:


heielec@t-online.de

It doesn't cost anything to ask! :D

[jeroldharter]

[QUOTE=Sal Santamaura;

It doesn't cost anything to ask! :D[/QUOTE]

You must be divorced.

Just kidding, but I have lost any arguments asserting just that. Thanks for the information.

[jon.oman]

I have an old Omega DII that I would like to convert. This is good information......

[Sal Santamaura]

You must be divorced...Not yet. First wife; 37+ years so far. And we moved to California 34 years ago too. :D