Experimenting with LED lighting for Durst M605

[psvensson]

I thought others considering LEDs for their enlarger heads might find this story useful:

The halogen bulb burned out in the color head of my Durst M605, so I replaced it with a new 100w "EPJ" lamp, intended for projectors. It worked, but it was too bright for my taste and much brighter than the old, unmarked bulb. I got exposure times of a few seconds at f8 with a 35mm neg enlarged to 5x7 on Kentmere VC (a fairly fast paper). And that was with the diffusor set to the dimmer 6x6 setting.

So I thought I might experiment with one of the new LED bulbs. I knew it would be less bright, which I wanted, and I also figured that the accuracy at short exposure times would improve, because the halogen bulbs take time to warm up and also glow for a short while after power is cut, whereas LEDs turn on an off instantly.

I bought a 2W warm white MR16 LED bulb one, said to be equivalent to a 20W halogen. It fit into the socket in the enlarger head with a little wiggling. It didn't burn out the transformer, and the light looked bright to me. But by the time it came through the diffusion box and the optics, it was barely visible on the baseboard - a real lesson in how inefficent the diffusor head is.

I gave LEDs one more chance. I bought a 4W cool-white bulb, figuring the added blue and overall higher efficiency as compared to warm white would help. It was significantly brighter, but it was nowhere close to bright enough. In fact, it was 9 stops dimmer than the 100W bulb! Filtering the light through a blue filter brought the difference down to about 8.5 stops, but that would still mean unacceptably long exposure times.

So it's back to halogens for me - I've ordered a 50W bulb. Now, what I really want is to build a head with banks of green and blue LEDs that can be switched independently for split printing ...

 

[BetterSense]

I got exposure times of a few seconds at f8 with a 35mm neg enlarged to 5x7 on Kentmere VC (a fairly fast paper).

Is this a problem for you? With my 6x6 Omega condenser enlarger I generally print 5x7s from 35mm at f/16 for about 10-20 seconds, through a grade 2 under-lens filter.

 

[paul_c5x4]

So it's back to halogens for me - I've ordered a 50W bulb. Now, what I really want is to build a head with banks of green and blue LEDs that can be switched independently for split printing ...

I too have been playing around with the use of LEDs. So far, it has just consisted of exposing a few scraps of VC paper to various coloured LEDs.. Calibrating the setup for specific grades is going to be one challenge, getting an even illumination across a 5x4 neg, another.

 

[psvensson]

Is this a problem for you? With my 6x6 Omega condenser enlarger I generally print 5x7s from 35mm at f/16 for about 10-20 seconds, through a grade 2 under-lens filter.

My lenses are visibly better at f4-5.6, so I generally don't stop down further than f8. But you have a point - on a 5x7 print, the difference probably isn't very big.

 

[K-G]

LED lighthead

It may be worth checking this link at the German company Heiland.
I don´t know what state this lighthead is in right now, but it certainly
looks interesting. Unfortunately I didn´t find any English translation,
so you may have to dig out your old German dictionary from the basement.
Good luck and best regards from

Karl-Gustaf Hellqvist

http://www.heilandelectronic.de/html/deutsch/produkte/kaltlicht_main.htm

 

[vdonovan]

I was only able to translate the first line: "Sie wollten schon lange Splitgrade® nutzen?" means "Are you one of those Splitgrade printing nuts?"

 

[paul_c5x4]

It may be worth checking this link at the German company Heiland.
I don´t know what state this lighthead is in right now, but it certainly
looks interesting. Unfortunately I didn´t find any English translation,
so you may have to dig out your old German dictionary from the basement.

Thanks for the link - Google/translate gives enough to make sense of the information. Particularly useful is the light density specs.. Blue 0.5cd/cm2, Green 0.7cd/cm2.
Gives me a ball park figure to aim for if/when I get the soldering iron out.

 

[philipp.leser]

The Heiland SplitGrade is distributed by RH Designs in the UK. They have an English description on their web page:

http://www.rhdesigns.co.uk/darkroom/html/heiland_splitgrade.html

The SplitGrade system has an excellent reputation!

Regards,
Philipp

 

[RobertV]

The Heiland LED cold light source is ready to fit on almost all enlargers.
from 24x36mm, 6x9cm, 4x5" till on special request 8x10".

Here is the English translation:
Dead Link Removed