The lamp in my enlarger just died with a quiet 'plink'. Enlarger lamps are typically 'overvoltage' lamps that run at a much higher temperature than conventional incandescents, their life span is measured in tens, at best 100 or 200 hours. They also have a bulb with a particularly thick opal layer for the smoothest possible light distribution.

Does anyone know exactly what color temperature those put out? And how much light an 150w one would do?

I yoinked a random 800lm LED lamp from a random fixture in the house and screwed it in, and i had to overexpose a stop to get roughly the same prints - so i reckon the 150w lamp must put out 1500-2000lm, but a direct comparison is impossible due to the difference in color temperature between a 2700k LED lamp and an overvoltage'd incandescent lamp.

The color temperature and CRI are important because standard black and white photo paper makes use of two differently sensitized types of silver halide, each having their sensitivity peak at a different part of the spectrum, each for a different amount of contrast in the picture. With color filters you can put the average spectrum towards the low contrast or the high contrast sensitivity peaks of the silver halides. If the lamp has a 'weird' spectrum, then the steps between each contrast filter won't match up anymore with what they should be.

LED lighting for multigrade printing has been available for a while now on the extremely high end enlargers. I am not a high end print maker, but i would like to have a longer term solution than to rely on one single manufacturer that still makes incandescent enlarger lamps. Old stock is available to a degree, but those are designed for a mains voltage of 220v, and i have 240-245v reducing the already short life span of those lamps even more.

LED has my preference, because i'll be able to take my sweet time focussing, selecting pictures to print by the gentle light of the enlarger itself etc without burning up the lamp.

Hi Laurens

Here you go. See the extract of the Philips 1984 catalogue from James’s Homepage.

Btw. Your ballast is sent to you. 

Cheers

Thanks!

2500lm, that's quite a lot of light. They don't stock those at the usual shops here. I'll go order one.

Do think that these are still available? I haven’t seen any in shelfs for decades. 

Hi Laurens

Here you go. See the extract of the Philips 1984 catalogue from James’s Homepage.

Btw. Your ballast is sent to you. 

Cheers

I thought that the CCT of the Photocrescenta is 3200K.

Do think that these are still available? I haven’t seen any in shelfs for decades. 

Incandescent enlarger lamps are still made by/for Dr. Fischer. At 15 euro the price is not too bad, if the entire led thing turns out to be unworkable i'll still get one. However, i'd like to see progress in the world of dark room printing so we're not stuck with just the options of old stock or a single manufacturer/reseller, with big issues if that one goes under. On older forum posts from before Philips shuttered all their incandescent manufacturing, the price was around 5 euro a piece. For that money it's of course not worth it to spend money on photo paper to do all kinds of tests. I would like to be another data point in the modernisation of darkroom printing though! My dream is to make an automatic exposure system. Most cameras have that by default, but only very few enlargers have it because the assumption is that once you've dialed in the enlarger exposure, the assumption is that your negatives are all exposed the same so only adjustments 'by eye' are needed. In my case i use many different cameras, some don't even have exposure controls at all!

I've searcherd around some more, and a few individual dark room printers report good results with 4000k lamps. They, however, do not report the exact type number of the lamp (Osram Parathom is mentioned) so i cannot look up the spectral distribution or CRI of those things.

I have now ordered a >90 CRI 4000k lamp with a plastic base (so it doesn't have filaments - those don't have the right light distribution pattern): https://www.budgetlight.nl/philips-corepro-led-lamp-e27-peer-mat-12-5w-1521lm-940-koel-wit-beste-kleurweergave-vervangt-100w-8719514329706

Technically it's 1000lm short of the Photocrescenta, we'll see how it goes. As of yet i haven't found 2500lm LED lamps in a matte/opal bulb that aren't HID replacement lamps (and therefore don't fit in the space within the enlarger). I have a hunch that the extra blue from the pump diode has a speeding up effect on the paper, since i barely had to expose 1 stop more with the 800lm 2700k lamp i tried, which is very counterintuitive.

I thought that the CCT of the Photocrescenta is 3200K.

There probably are different types of Photocrescenta. The extract above shows a lamp with a higher CCT but only 3 hours of life. Mine is the standard 150w model.

Aren't Photocrescenta 3200K 100 hours, Argaphoto 3200K 100 hours, Photolita 3400K 3 hours?

No.  If you would read the uploaded link, you can see that Photocrescenta was available in different CCT’s and with corresponding life differences.

@Laurens You can take a standard general lighting lamp and overdrive it by say, 20% of nominal voltage. You'll get exactly what photo lamps are made for - a short living light source with high CCT.

Almost, but not quite. A standard matte GLS lamp still has a bright spot where the filament is. I have to verify, but i think my Meopta Opemus 6 does not have a separate diffuser aside from the little bit of ground glass in the contrast filter holder.
It would be an option if i would be able to very carefully cut off the bottom 3rd of the Photocrescenta lamp, and cement that to the GLS lamp, or make another kind of heat resistant diffuser.

I do have a 100w "soft" lighting lamp in stock with a very similar truly smooth 'opal' bulb. That thing will work exactly like you suggest. But those cannot 'just' be bought here anymore, you gotta find them at thrift shops.

I have now received my 1000lm 3000k and 1500lm 4000k 90cri LED lamps, i'm gonna try and see how well those work.
_{(aside from that, also an osram 2200k 90CRI led lamp which gives really nice light, i might buy a whole lot of those!}

I suppose one of the old Philips Softone type lamps in T-shape bulb may work rather well - especially since the flatter top of the bulb may direct more light into the enlarger’s optics.

In the 1970s Philips experimented with enlarger lamps having reflector shape bulbs (R80, R95) for exactly that reason, to improve optical coupling.  No reflector coating, just a heavily coated opal white bulb.  Some were sold, I have an old 150W R95 3000K, but it seems they were not popular and withdrawn a few years later.