Swap Opal Incandescent Bulb with LED Bulb?

Newt_on_Swings · Mar 1, 2013

Yesterday I swapped out a broken LPL 6700 enlarger with a simple two condenser lens (similar to Leitz focamat type, Mars 66 made in Japan brand) enlarger in the darkroom where I teach. It was brand new in the box, and was the only complete enlarger setup in storage, so better a older working enlarger than a empty enlarger station. It fires up and works fine, but the lamp house heats up quickly and gets quite hot especially with extended focusing times. Since I teach a number of kids in this darkroom routinely, I thought a cooler LED solution would be safer.

Has anyone swapped out the typical opal enlarger bulb with an LED type? I am curious if the little LED bulbs that are clustered to make the entire bulb, gives off light that is not even enough for enlarging. I have seen a few LED bulbs in stores, but I can clearly see the smaller LEDs under the diffusing cover clearly when lit up. Because this is a condenser type do you think there is a chance that this would affect the output when printing?

Also should I look for a warmer or cooler color temp bulb? We use variable contrast papers mainly.

Thanks in advance.

ac12 · Mar 1, 2013

I think the LEDs will give you trouble with VC paper.

Check the bulb rating of the enlarger.
Some will take 150w bulbs, others max at 75w.
If it is getting HOT, and you have short exposure times, I think you have a bulb that is too big for the enlarger. Drop down to a lower wattage bulb, and it will run cooler.
My Durst M600 is rated for a 150w bulb, but I use a 75w bulb in it, and sometimes I which I could find a 40w photo bulb.

Newt_on_Swings · Mar 2, 2013

Well the setup doesn't get super hot right away, but I think if left on for a more extended time, such as when a new student first uses a grain magnifier or if they are trying to figure out how best to place the image on the easel, or test different magnification of the image, or practicing dodging and burning certain areas, the enlarger can potentially get hot to the touch. A 40w opal photo bulb would probably work pretty well. Right now a 150w bulb is installed as it was the last photobulb size in the darkroom, all the rest are the double pin type bulbs. I have not had any students use it yet as I installed it at the end of the day.

madgardener · Mar 2, 2013

I agree with the comment about LED bulbs, the claim is that they do as good a job as traditional bulbs, but my experience (not with enlargers) is that they aren't as bright and the light is a lot harsher to the eye.

Perhaps instead of LED, maybe you could try a CFL?

David Brown · Mar 2, 2013

I don't know for sure, but my guess is that as a medium format enlarger it should probably have a 75 watt bulb. I would try that first.

tkamiya · Mar 2, 2013

I use a pair of Omega D2s and they have 75 watts bulbs. When I had an 150 watts in there, it got EXTREMELY HOT and they were too bright. With 75 watts, extended focusing doesn't give me any issues. It does get warm but not overly or dangerously so. That may a cheaper and better alternative. I can print both 35mm and medium format for reasonable size with no issues.

Ian C · Mar 2, 2013

A properly designed condenser enlarger has light-baffled air vents at the bottom and top of the lamp house. As air inside the housing heats, it rises upward and out of the upper exhaust vents. That rising air flowing out of the upper exhaust vents causes cooler ambient air to be drawn in through the lower air intake vents. This air flow limits the temperature inside the housing to a safe level.

For example, I have a Beseler 23C II enlarger equipped with the 75-watt PH-111 opal photo lamp. When the lamp is left on continuously for several minutes the housing gets warm, but not excessively so. The heated air flow rising out of the vents is noticeable by placing my hands above the vents. Even after several minutes of continuous operation the surface of the housing is warm to the touch, but not dangerously so. The cooling system is adequate to keep the lamp house at a safe temperature.

The maximum temperature inside the housing is proportional to the current rating of the bulb. It would be prudent to check the following (some of which have already been cited in previous posts):

1. The current rating of the bulb. This type and size of enlarger (probably 6 x 6cm given the name “Mars 66”) is most likely intended for a 75-watt opal photo lamp. If the lamp installed is of a higher current rating, changing the bulb will lower the operating temperature of the enlarger.

2. Verify that the air vents are not covered with something, such as packing material.

3. If it still runs too hot, you can install a variable bulb dimmer intended for conventional incandescent bulbs in the AC line. With this, you could reduce the current to the lamp to limit the heat to a tolerable level. Here’s an example that could be installed into a simple box housing and is inexpensive.

http://www.lbclighting.com/d-600r.h...dom=Shopping&gclid=CLKJmYWj3rUCFag7MgodpAoAPA

Newt_on_Swings · Mar 2, 2013

Ah thanks for the suggestions. I suspected the 75w lamp would have been the right size. The enlarger did not have a manual and only a promotional ad pamphlet with only 1 picture on it. I did not remember seeing vents but I could be wrong, I'll double check.

You are correct it is a 6x6 enlarger, it comes with a 6x6 carrier as well as a 75mm lens preinstalled. It also came with a 35mm neg carrier and 50mm lens. I forgot the brand of lens but they were 25mm thread.

I will pick up a 75w bulb, b&h has them online for less than $5, maybe they have them in store too.

If I get a chance I would like to try out the CFL and LED options and test it, but I have a feeling that those bulbs are just not frosted/opal covered enough to eliminate hot spots in a condenser setup. As well as the potential difficulties with using vc papers. I really thought someone atleast had tried this with one of their enlargers.

Roger Cole · Mar 2, 2013

Yes, but not as simply as swapping the bulb. There was someone posting both here and on LFPF and making very nice replacement Omega D lamphouses using careful color matched LEDs. I bought one and love it. Evennness is at least equal to what I get with a 211 or 212, VC response to filters seems the same, there is virtually no heat and no worries about negative popping and the lamp life is rated at something like 30k or 35k hours. Brightness is just about evenly in between a 75W 211 and a 150W 212, which is fine for my work. See the thread here:

(there was a url link here which no longer exists)

This may not help you much for what you want to do, granted. You could always just try it. Worst that happens is that it doesn't work well and you waste a few sheets of paper testing.

bernard_L · Mar 2, 2013

Thumbs down on CFL: takes time to reach nominal brightness. From minutes (cheapos) down to seconds (better brands), but still too long to assume constant light output.

cliveh · Mar 2, 2013

I dont see why an LED lamp shouldnt work. In general I have replaced some room lighting with these and a 7 Watt LED is as bright as a 50 Watt. They also look whiter and are much cooler. Students dont just have enlargers on for longer periods of time when dodging etc. They often just leave them on and leave the darkroom. You could cook an egg on some of those enlargers after a few minutes. I have never tried an LED bulb in an enlarger, but it may be worth experimenting.

MartinP · Mar 2, 2013

The LED bulbs cost three times as much as a normal enlarger bulb over here and have the individual LED's clearly visible - not like the very smooth blob of light which a condenser enlarger is expecting to 'see'. Most practical option would probably be to simply buy a few of the correct rating bulbs, and also check there is nothing blocking the cooling vents I suppose.

tkamiya · Mar 2, 2013

Newt_on_Swings said:
If I get a chance I would like to try out the CFL and LED options and test it, but I have a feeling that those bulbs are just not frosted/opal covered enough to eliminate hot spots in a condenser setup. As well as the potential difficulties with using vc papers. I really thought someone at least had tried this with one of their enlargers.

I can try this next time with a CFL bulb if you wish. I'd imagine I will have some challenge because of the time lag for coming on full strength and some after glow after it's turned off. As to LED, I'm concerned about the spectura VC papers/filters require. It'll be an interesting experiment that I don't mind doing myself.

Somewhere on APUG, there was a post from someone who made his own "cold head" with LED matrix.... I remember he used two different colors and ultra-violet.

Newt_on_Swings · Mar 2, 2013

Well I was reading into the possibility of CFLs but even with the newer hybrid instant on types, they still take up to 30 seconds to reach full brightness, so I think they are pretty much out of the question.

bdial · Mar 3, 2013

There was some discussion some time ago on using CFL's. As I recall the method most used was to keep the light on all the time, and control the exposure with the lens cap or a shutter.
I have a couple of LED bulbs that look like they could work in an enlarger, they have a pretty dense white plastic dome over the LEDs. Haven't tried it for that, however, as my enlarger doesn't have a screw base lamp.

Ronald Moravec · Mar 3, 2013

bdial said:
There was some discussion some time ago on using CFL's. As I recall the method most used was to keep the light on all the time, and control the exposure with the lens cap or a shutter.
I have a couple of LED bulbs that look like they could work in an enlarger, they have a pretty dense white plastic dome over the LEDs. Haven't tried it for that, however, as my enlarger doesn't have a screw base lamp.

Yes, what we did with "cold lights" a long time ago.

Take care that whatever you use, it puts out light of the correct color temperature for the paper in use. LED I have seen are very blue, ok for graded paper or to get max contrast ONLY on VC. For low contrast on VC, you will need 2800 K wave lengths, ie yellow, to be available.

There may be warm LED available now. Go to Home Depot and check out their display.

Like to add fluorescents are spiky in spectrum and not continuous so there could be missing wave lengths that you need. Split grade printing might be the answer.

Newt_on_Swings · Mar 8, 2013

Just a quick update, I got a pair of the opal 75w bulbs from B&H and ran the enlarger for 15min with it on and it only got to a warm level so very safe for my students who got a chance to print with it today. Nice crisp prints with its factory lenses stopped down. The brand of lenses was also Mars branded. I am still on the lookout for a nice bright LED alternative though and will report back once I get some time to shop around.

jlpape · Mar 8, 2013

Newt_on_Swings said:
If I get a chance I would like to try out the CFL and LED options and test it, but I have a feeling that those bulbs are just not frosted/opal covered enough to eliminate hot spots in a condenser setup. As well as the potential difficulties with using vc papers. I really thought someone atleast had tried this with one of their enlargers.

If you still want to go the LED route, possibly the instructor in the shop class (if your school has one) could cut a piece of translucent plexiglass for you to mount at the base of the lamp housing, or rest on top of the condensers. May help with the hot spots.

Also, If you are interested, I posted on the topic of VC papers and an LED bulb with some measurements. My net, at least for the LED source that I was using, is that the LED does change the characteristic curve of exposure vs density a bit, but not enough to rule out their use on a practical basis. Especially if these are students learning for the first time. More seasoned printers would probably apply more scrutiny.
(there was a url link here which no longer exists)

Swap Opal Incandescent Bulb with LED Bulb?

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