LED replacement for incandescent in condenser enlarger?

[Fr. Mark]

The Beseler 45M I bought came with a dead lamp. OEM was a ?100? Or 150? Watt opal frosted lamp. Is there a good LED bulb that's a screw in replacement? Do I need to worry about color temperature of the bulb with multi grade paper? I tend to prefer 6500K bulbs---daylight balanced because otherwise paintings started outdoors look wrong when I finish them inside. Also, it makes studio work with Ortho film work better/more like outdoors. But maybe it's wrong in an enlarger for multi-grade paper.

Eventually, I'm planning on making a diffusion head or three for this enlarger: 4x5 and smaller, 5x7 and 8x10 based possibly on an LED panel. So I can print from bigger negatives, etc.

Thanks.

[LabRat]

I had considered converting condenser + color head enlargers over to LED, but I realized there was a problem... That color heads required a 3200K halogen bulb, and a incandescent condenser's bulb is a little under (but around) 3100K... So color materials would need a overall correction filter (that would cut light output) and it would throw off the multigrade B/W scale, as those papers depend on changing the ratio of the green and blue light (for the paper's green and blue sensitivity emulsions)... And we would have to check/test different make LEDs as their color balance could be slightly different now, or later obtained... So all scales would have to be re-calibrated...

Lamps are rich in output on the red end of the spectrum, and fall off towards the blue end... (That's why your exposure is so long when using a hard PC filters... Most of the light is "wasted" as more is "cut-off" just to use the blue, with more and more cuts to the green (flatter contrast layer) when harder contrast is required...) The PC filters are matched to the lamp & paper's curve...

So you would have quite a time re-balancing this after installing a unknown LED lamp...

But possible!!! For the time being, buy some PH212 bulbs (150W)...

Steve K

[BetterSense]

I don't think this is going to work out. The light distribution and spectrum of LEDs are too different. I fear that you will just cause yourself problems trying. Track down some proper incandescent replacements.

[Fr. Mark]

I will say that using a 6500 or 5000k LED light bulb (I forget which) made for extremely short contact printing times under the enlarger at f22 with a 161mm lens most of the way up---5 sec and almost totally black. It is a 60W equivalent, iirc, not 100 or150W eq.

Over on the other enlarger, a 50 mm lens racked up to where it'd make a 10x enlargement, at f8, contact printing times were running 20-40 sec depending on 4x5 Negative density. That one has a smaller wattage ??60??75?? Opal enlarger bulb thru a condenser.

I'm not looking to do color printing and I would rather not have to deal with the heat generated by incandescent lamps which are probably in short supply. LEDs would be a lot easier to design a diffuser around---I could use materials that would never hold up to the heat of 150W incandescent.

But, as I thought, there are going to be issues with color matching for MG papers. I've done very little printing so I'm not worried about "re calibrating." But, it's looking like you are right that I will need to find LED's that have a much lower color temp and, if possible a smooth spectrum, to make MG work.

Anyone out there done this successfully?

[jose angel]

Old wives`tales...
I also used to be worried about the spectrum, color balance and all this "theoretical" issues until the day I bought one; since then, I simply use LED (my choice are 2800-3000ºK). Right now, I`d say they work much better than tungsten ones.
Just give them a try; I bet the only problems you could find (if any!) will be related to illumination evenness and output power. On a Beseler ("direct light throw" type), they should work perfectly fine if you don`t print too large. With reflex enlargers things are not that easy, although I also use them.
Another topic could be the size of the lamp housing; bulbs use to grow in size with power, highest power ones are slightly bigger than ordinary tungsten ones, so some of the -highest- powered bulbs may not fit inside the *smallish* Beseler housings.

[LabRat]

What "re-calibrating" means is that, let's say you are using a PC/MG #3 filter (or other), it will not be that, but something else (that you probably can get a handle on), but the filter "steps" you are used to will be different... If you use a color head for PC/MG, you would test and learn the new filter settings, but the linearity of the old "steps" would change...

Yes, you will have a faster printing time, as the LED's have better output in the blue/green end of the spectrum... How even the transition between blue/green remains to be seen...

The other thing you have to look at is the old bulb height from the socket... The opal diffusing surface on the old bulb was a critical distance from the top of the condenser, as this diffused light focused from the bulb had to be at an exact point or issues with coverage of the neg below, or fringing, or "kidney bean" shapes would interfere with the overall coverage... If you install a diffuser, it just has to be evenly lit, and at the same height as the old bulb...

I'm completely hooked on using a "hot" lamped dichroic color head for B/W PC/MG printing mounted over the condensers where the bulb was...
Using a color head for MG/PC is a hot tip... (Check #16 of this post

http://www.largeformatphotography.in...usion+enlarger

I hope to replace this with LED someday, as it does run hot, and when time to re-lamp, not too cheap... But the bulbs last a long time!!!

Steve K

[Tin Can]

I missed that diffusion condenser thread.

Beseler grey CB7 4X5 early model had AGFA Color head with 'non Dichro' 3 color filter system on top of condensers.

Later they removed the condensers and used a blue Dichro DG colorhead. I have both models.

I mostly use a Beseler blue condenser head 45MCRX.

Obviously the factory tried all variations and we should too.