500 Watt enlarger bulb? [Archive] - Large Format Photography Forum

Jac@stafford.net

27-Dec-2014, 20:04

Does anyone know if this would work for a condenser enlarger? (For Saltzman 8x10). Mogul base converter available.

It is so reasonably priced I can buy and try, but I thought I'd ask the net wisdom.

The bulb here: https://www.1000bulbs.com/product/284/IN-0500PS35F.html
.

Tin Can

27-Dec-2014, 21:01

I don't know, but I ordered 1 with Satco adapter. It may be useful in several ways here.

Also notice the CFL equivalent is almost as powerful.

Jac@stafford.net

27-Dec-2014, 21:03

Check out the anticipated life of that bulb.
"2,000 Life Hours"

Do you think it is a typo?

vinny

27-Dec-2014, 21:13

As long as its frosted enough, I don't see why not. The mogul adapter will change the position of the bulb slightly but not much.

Tin Can

27-Dec-2014, 21:23

Check out the anticipated life of that bulb.
"2,000 Life Hours"

Do you think it is a typo?

No, it's a 130 volt bulb for USA 120 volt, so 2000 life hours may be possible and it seems users are large rooms with high ceilings like a Church. They want long life bulbs.

However it does need venting, or it's going to be an electric heater. Venting on an Elwood is minimal and I may add an exhaust fan.

I will try it. Focus fast, turn it off, let it all cool down and of course use double glass neg carrier.

I had a line on 2 big Durst condensers at Central Camera but the shop meddled the middle and they disappeared. :(

If it doesn't work for me, it will be great for lighting effects.

I have a few long neck 250 and 500 watt enlarger bulbs, they don't last long.

This bulb is long but the neck looks kinda short for the Saltzman adjusting system, which is a collar around the bulb's neck.

Gotta buy it and try it.

Tin Can

27-Dec-2014, 21:25

As long as its frosted enough, I don't see why not. The mogul adapter will change the position of the bulb slightly but not much.

Gotta see how bad the writing is on the bulb top. Sometimes it can be scraped or sanded off.

StoneNYC

28-Dec-2014, 00:31

Never mind

StoneNYC

28-Dec-2014, 00:35

Seems like a few options, found this one.

http://www.garvinindustries.com/lighting/led-cfl-lamps/led-cfl-replacement-lamps/mogenlg?gclid=Cj0KEQiAzvmkBRCm3ZbV-4-hwrYBEiQAgLOw67S9GcmqC6nyYx15kBiE22pN0roUSAcr5nGzMxywudMaAgYP8P8HAQ

So do you think a certain version of the adapter would be necessary because of the high wattage bulb? Or should they all work just fine?

The adapter shouldn't interfere with the bulb position since the connector is floating anyway.

Sevo

28-Dec-2014, 04:12

At 2000hr life, it is probably going to be less bright than a 250W enlarger bulb, but much hotter - this could be a danger for your negatives. I don't know by how much the bulb can be moved in that enlarger, but the difference in filament position between the original and replacement bulb (including all adapters needed and any size difference) MUST be small enough that the filament can be repositioned into the condenser focus, or it will not do.

ic-racer

28-Dec-2014, 05:02

I use standard-base 500W ECT bulbs in my hot-lights. The frosting gets black after a while, even though the filament still works fine for many hours.

vinny

28-Dec-2014, 07:04

Those are the ones we use for motion picture use and I think they would be fine for this use too but I don't know what the ventilation is like on this enlarger. Look for a ceramic version to be sure.

Seems like a few options, found this one.

http://www.garvinindustries.com/lighting/led-cfl-lamps/led-cfl-replacement-lamps/mogenlg?gclid=Cj0KEQiAzvmkBRCm3ZbV-4-hwrYBEiQAgLOw67S9GcmqC6nyYx15kBiE22pN0roUSAcr5nGzMxywudMaAgYP8P8HAQ

So do you think a certain version of the adapter would be necessary because of the high wattage bulb? Or should they all work just fine?

The adapter shouldn't interfere with the bulb position since the connector is floating anyway.

Jac@stafford.net

28-Dec-2014, 09:14

At 2000hr life, it is probably going to be less bright than a 250W enlarger bulb, but much hotter - this could be a danger for your negatives. [...]

Thanks, Sevo. Silly me: I equated Watts with brightness. I'll spend the rest of the morning learning up. Already it is clear that given only lumens, we cannot calculate watts, nor visa-verse.

I see from 1000bulbs.com such metrics as lumen, watt and candle power, but not all for each bulb so I must learn which metrics matter most and how to convert, if possible.

StoneNYC

28-Dec-2014, 09:47

StoneNYC

28-Dec-2014, 09:55

Those are the ones we use for motion picture use and I think they would be fine for this use too but I don't know what the ventilation is like on this enlarger. Look for a ceramic version to be sure.

Thanks, ceramic, looking...

Nope, all the ones that start as a medium and go UP to a mogul are plastic...

At least this one lists the maximum wattage...

http://www.bulborama.com/MEDIUM-E26-TO-MOGUL-E39-SOCKET-ADAPTER-INDUSTRIAL-GRADE-p2216.html?AdID=13820cm00cm0H00736&gclid=Cj0KEQiA8f6kBRCGhMPFtev8p58BEiQAaMLmqdFTZ7lesdG3IvGc-jVaPW8roCFuUVfYI8iDl30gWscaAjxD8P8HAQ

Since we are going to be permanently switching to using a Mogul base, I think it might just be easier to re-wire for a mogul socket... It's just a dangling wire...

127263

There is poor ventilation but a fan could easily be added.

ic-racer

28-Dec-2014, 10:14

Stone, sorry if this was mentioned, as there are hundreds of posts on your enlarger, but the wires look to have asbestos covering to me. The asbestos is rougher and not a smooth as fiberglass weave covering.

Sevo

28-Dec-2014, 10:17

I must learn which metrics matter most and how to convert, if possible.

As long as you use one unit for comparison (or convert), it does not matter whether you use Lumen or Candela, or candle power.

Watts are quite meaningless when it comes to the light output - watts are determined by the resistance of the filament, and a long thick filament will have the same total electrical resistance as a short thin one, while each mm of it will heat to a much lower temperature. The filament temperature controls the proportion of visible light emitted besides the infrared (i.e. brightness), and the evaporation of filament metal (i.e. life time). Within practical limits "fast burning" (10h) photo lamps have about 50-70% higher light output than equally powered "long life photo" or general purpose household incandescent lamps, and more than twice that of long life utility lamps of identical electric power.

Moving up to a lamp that has higher electrical power than the original always is a risk - the extra power is emitted as heat, and given that most enlargers were designed to be safe with the heat output from the original wattage, but little extra margin, you'll risk the negatives, enlarger, or even a fire.

ic-racer

28-Dec-2014, 10:28

I don't know if you guys have seen these mogul based PIZZA lights. A diffuser screen over this and it might work well with the condensers.

BTW, I just got my first condenser enlarger to play with. It is a unique additive Philips color condenser head. The three dichroic reflector lamps shine on a white translucent disk. The white disk serves as the focus point for the condensers (rather than the frosted globe of a bulb). The orientation of the lamp to the condensers reminded me of a small version of your Saltzman condenser head.

127265

http://img.photobucket.com/albums/v670/ic-racer/497bb6d1-7854-493e-9d66-877e99e4d370.jpg

StoneNYC

28-Dec-2014, 10:29

As long as you use one unit for comparison (or convert), it does not matter whether you use Lumen or Candela, or candle power.

Watts are quite meaningless when it comes to the light output - watts are determined by the resistance of the filament, and a long thick filament will have the same total electrical resistance as a short thin one, while each mm of it will heat to a much lower temperature. The filament temperature controls the proportion of visible light emitted besides the infrared (i.e. brightness), and the evaporation of filament metal (i.e. life time). Within practical limits "fast burning" (10h) photo lamps have about 50-70% higher light output than equally powered "long life photo" or general purpose household incandescent lamps, and more than twice that of long life utility lamps of identical electric power.

Moving up to a lamp that has higher electrical power than the original always is a risk - the extra power is emitted as heat, and given that most enlargers were designed to be safe with the heat output from the original wattage, but little extra margin, you'll risk the negatives, enlarger, or even a fire.

I would worry more about the fire, the negatives in these things are so far removed from the light source I can't imagine the heat being enough to get that far down the line, however a fire is possible. But it's basically a metal box. So not much to catch on fire, it would need to be hot enough to melt the metal.

Jac@stafford.net

28-Dec-2014, 10:41

Stone's enlarger appears to be the one linked to below which uses the incandescent bulb rather than their preferred cold light head. Scroll down the image to see the head without showing the 14" condenser unit.

http://www.digoliardi.net/saltzman-30-wac.jpg

Model 30 WAC

Jac@stafford.net

28-Dec-2014, 10:50

As long as you use one unit for comparison (or convert), it does not matter whether you use Lumen or Candela, or candle power.

Indeed, but in the online catalog they use Watts OR Lumen OR Candela. There's no way to determine Lumen or Candela from Watts. :(

Sevo

28-Dec-2014, 11:00

Indeed, but in the online catalog they use Watts OR Lumen OR Candela. There's no way to determine Lumen or Candela from Watts. :(

I'd assume that anything merely rated in Watts was not intended for applications where amount and quality of the light is critical - and probably will have correspondingly irregular illumination. Regular illumination is the key point for which I'd look in a enlarger lamp - original lamps used a opalescent white coating, at the loss of 70-80% of their light output. While substitutes won't be quite as good if you have a enlarger for which no opalescent bulbs are made any more, they'd be better as good as possible. We don't have quite the same issues over here (there still is a maker of proper enlarger lamps in Germany, within the 150-250W power range my enlargers take), but if I had, I'd settle for something fit for theatrical or showroom spotlight use rather than bulbs not made for any kind of optical system at all...

StoneNYC

28-Dec-2014, 11:28

127267

Original style bulb.

StoneNYC

28-Dec-2014, 11:33

Found the info!!!!

This is the Phillips version of the GE bulb...

Appears to be 11000 lumens

http://www.donsbulbs.com/cgi-bin/r/b.pl/ph302-125v~ansi.html

And detail sheet...

127268

Sevo

28-Dec-2014, 11:45

In doubt I'd settle for 250W rather than use a fundamentally different lamp type - a smaller lamp might require a different rod to be properly positioned, and show some light falloff near the edges, but a lamp missing the white coating will be much worse. You might want to write Dr. Fischer (info@dr-fischer-group.com) whether they make or might make a lamp of the above characteristics - they seem to be the only current maker of white coated enlarger lamps.

Jac@stafford.net

28-Dec-2014, 12:21

Pardon my ignorance, but if a bulb has L luminance, then do three bulbs make 2L or 3L?

IOW, is it like flashbulbs where 3 bulbs = 1 stop increase (over 1) and 7 bulbs make 2 stop increase, or not?

Larry Gebhardt

28-Dec-2014, 12:24

Thanks, Sevo. Silly me: I equated Watts with brightness. I'll spend the rest of the morning learning up. Already it is clear that given only lumens, we cannot calculate watts, nor visa-verse.

I see from 1000bulbs.com such metrics as lumen, watt and candle power, but not all for each bulb so I must learn which metrics matter most and how to convert, if possible.

I bought a bulb by accident that is similar, but not frosted. It's also has specs for 130 and 120V. At 130V it's 500Watts, 5000 hours and 7800 lumens. At 120V it's 440Watts, 12500 hours and 5896 lumens. My guess is the ratio between your bulb and the one I have will be about the same. So it may not be too bad.

With a Variac you could run it at 130V, or 125V, or 110V (and make it last a lifetime).

Edit: Also, with a condenser enlarger the diameter of the bulb as well as the evenness of the frosting will be very important.

Jac@stafford.net

28-Dec-2014, 13:02

Larry, which Variac model do you use, please?
.

Len Middleton

28-Dec-2014, 15:01

ic-racer

28-Dec-2014, 16:10

For a 500W enlarger lamp, a minimum 500W variac should work. I have an inexpensive Chinese 1000 Watt TDGC-1KM that seems to work well for my other projects. I have not used it with an enlarger, but I have used it to dim hot-lights between shots.

Larry Gebhardt

29-Dec-2014, 08:07

Larry, which Variac model do you use, please?
.

It's similar to this one off ebay: http://www.ebay.com/itm/Variac-Variable-AC-Power-Transformer-0-130-VAC-with-Meter-TDGC-2KM-/161466126380?pt=LH_DefaultDomain_0&hash=item259821902c

It might be the same, but with this type of knock off gear I'm never sure. it works very well, but the marked voltages are not accurate. I used a meter and made marks at the voltages I'm interested in.

Larry Gebhardt

29-Dec-2014, 08:08

Different voltages may result in a colour shift, hence the use of constant voltage transformers with enlargers.
An issue in colour printing but not certain if the colour shift would be enough for a problem with VC paper...

I found a very slight effect on VC paper when dropping the voltage down to 90V. Surprisingly it was only about half a grade.

Len Middleton

29-Dec-2014, 08:46

Larry,
Thanks for the info, as I was curious about that,
Len

Tin Can

31-Dec-2014, 12:32

No, it's a 130 volt bulb for USA 120 volt, so 2000 life hours may be possible and it seems users are large rooms with high ceilings like a Church. They want long life bulbs.

However it does need venting, or it's going to be an electric heater. Venting on an Elwood is minimal and I may add an exhaust fan.

I will try it. Focus fast, turn it off, let it all cool down and of course use double glass neg carrier.

I had a line on 2 big Durst condensers at Central Camera but the shop meddled the middle and they disappeared. :(

If it doesn't work for me, it will be great for lighting effects.

I have a few long neck 250 and 500 watt enlarger bulbs, they don't last long.

This bulb is long but the neck looks kinda short for the Saltzman adjusting system, which is a collar around the bulb's neck.

Gotta buy it and try it.

Got the bulb today. It is very lightly frosted, nothing like a real enlarger bulb. It has printing on the dome top, that could be removed. It is very bright. Staring at it, the filament was not visible, just a very intense 2" ball of light. It will not be good for an Elwood, it may be OK for a condenser head as it is a wide ball single point of light.

Jac@stafford.net

31-Dec-2014, 13:19

Got the bulb today. It is very lightly frosted, nothing like a real enlarger bulb. It has printing on the dome top, that could be removed. It is very bright. Staring at it, the filament was not visible, just a very intense 2" ball of light. It will not be good for an Elwood, it may be OK for a condenser head as it is a wide ball single point of light.

I wonder if this stuff could be applied to the bald patch on the bulb. It might be worth experimenting.
http://www.dickblick.com/products/delta-glass-paint/

Tin Can

31-Dec-2014, 13:36

I wonder if this stuff could be applied to the bald patch on the bulb. It might be worth experimenting.
http://www.dickblick.com/products/delta-glass-paint/

Cheap enough and I went right by Blick yesterday on my monthly shopping trip. I rent a Zipcar once a month for shopping. So it will not be for another month.

Oven proof is a start. I already stored the bulb for later, I should have measured the surface temp...

However the printing stands proud and may razor blade off easily. Razor blades are great as scrapers, I often use them at 90 degrees to a surface and scrape.

StoneNYC

31-Dec-2014, 14:34

Got the bulb today. It is very lightly frosted, nothing like a real enlarger bulb. It has printing on the dome top, that could be removed. It is very bright. Staring at it, the filament was not visible, just a very intense 2" ball of light. It will not be good for an Elwood, it may be OK for a condenser head as it is a wide ball single point of light.

If you can stare at it and not go blind it's not bright enough, the 500W Saltzman condenser bulb was so bright I couldn't event look sideways NEAR it.

Luis-F-S

8-Jan-2015, 20:32

John Kasaian

9-Jan-2015, 12:12

500 watts would be great for warming tortillas. Hey, it's nearly lunch time!:)

Larry Gebhardt

9-Jan-2015, 19:48

Can also try a PH/303, 500 Watt, 120v, 6.06 inches in length - Diam 2.76 inches - Life hours: 20. They have a few left and not horribly expensive. With a Variac/Dimmer, can probably triple the 20 hr bulb life. Might be just what that Saltzman needs!

http://www.topbulb.com/ph-303-bulb-ph-303-enlarger-bulb

L

Run it at 100V and you'll get about 9 times the life. 90V and it's 31.

Formula is (Design Voltage / Actual Volatge)^12

Luis-F-S

12-Jan-2015, 12:13

Can also try a PH/303, 500 Watt, 120v, 6.06 inches in length - Diam 2.76 inches - Life hours: 20. They have a few left and not horribly expensive. With a Variac/Dimmer, can probably triple the 20 hr bulb life. Might be just what that Saltzman needs!

http://www.topbulb.com/ph-303-bulb-ph-303-enlarger-bulb

L
Checked this morning, they're all gone! Glad I bought my two. NOS, really thick coating. With those two and my 3 Thorn 300 W bulbs, I should be all set should I wish to go back to condenser printing with my Durst!

Tin Can

12-Jan-2015, 12:25

I bought 7, all they had. The price was very low. I will need them over the years as Elwoods eat them. I will be using them at 100 volts for B+W diffusion printing only.

They arrive today.

Tin Can

12-Jan-2015, 14:36

UPDATE

They are here. All the same GE part #, but some are an inch longer. Some say 6 hour life.

I bet TopBulb (http://www.topbulb.com/)could find more as they are located in Indiana, home of Elwood enlargers!

They will be used in my locally donated 8X10 Elwood and here for mural projection with both my 5X7 and 8X10 Elwoods.

127970

Larry Kellogg

12-Jan-2015, 14:38

Tin Can

12-Jan-2015, 14:47

Oh, well, you beat me to them. It must be possible to find a couple more.

I waited 2 days for somebody to step up. StoneNYC never showed either.

Also it was free shipping at $95 which cinched the deal.

Larry Kellogg

12-Jan-2015, 15:11

I waited 2 days for somebody to step up. StoneNYC never showed either.

Also it was free shipping at $95 which cinched the deal.

Ok, I'm an idiot, I missed them, I got there too late. If you want to sell one for $25, I'll take one. I did save you $60 on the Japanese screw drill. ;-)

Tin Can

12-Jan-2015, 15:21

Ok, I'm an idiot, I missed them, I got there too late. If you want to sell one for $25, I'll take one. I did save you $60 on the Japanese screw drill. ;-)

Sorry Larry, I'm not reselling them.

Call TopBulb and ask them to find more.

These are definitely NOT the last bubs in the world. I bet NYC has many. But where?...

Larry Kellogg

12-Jan-2015, 16:06

Sorry Larry, I'm not reselling them.

Call TopBulb and ask them to find more.

These are definitely NOT the last bubs in the world. I bet NYC has many. But where?...

Yeah, but where, that's a good question. Everybody kinda assumes NYC has everything, but rising rents and online retailers have pushed out a lot of little shops that might carry such items.

I sent a note to TopBulb asking them to try to find some more of those bulbs. I'll report back, after I buy a few. ;-)

Tin Can

12-Jan-2015, 16:23

Yeah, but where, that's a good question. Everybody kinda assumes NYC has everything, but rising rents and online retailers have pushed out a lot of little shops that might carry such items.

I sent a note to TopBulb asking them to try to find some more of those bulbs. I'll report back, after I buy a few. ;-)

I hardly consider seven 6 hour light bulbs 'hoarding'. However definitely not saying you said that at all.

Now if I bought 50, that would either be hoarding or a money making opportunity.

You WILL find them. I can practically guarantee it. Then buy and tell us later, as is your plan, is best.

Notice the same policies are followed by lens buyers. They tell us of the good deal after a purchase...

Luis-F-S

12-Jan-2015, 16:43

I would have bought more, but I seldom print with the condensers, and 500 watts is way bright for me. I'll dim this bulb way down if I need to use it and adjust for the color temperature change. Larry, I did give everyone fair warning.........L

Larry Kellogg

12-Jan-2015, 16:57

Nah, I never said you hoarded, Randy, I just said I would buy a few before posting that they were back in stock.

The people on here, including yourself, have helped me far more in terms of advice than the value of a few light bulbs. You win some, you lose some, no big deal.

Larry Kellogg

12-Jan-2015, 16:58

StoneNYC

12-Jan-2015, 17:30

I would need the king neck ones I think for the Saltzman, hmm missed them too, I would pay $25 for a long neck one too hahaha.

Larry Kellogg

13-Jan-2015, 07:49

I would need the king neck ones I think for the Saltzman, hmm missed them too, I would pay $25 for a long neck one too hahaha.

Good luck finding them. I did not receive good news from TopBulb regarding finding some more:

"Oh I am so very sorry the purchasing agent looked and looked and none of our vendor have any stock."

I'm good, I've got some other bulbs on hand, and I'm attached to my retinas, or vice versa. ;-)

Larry Gebhardt

13-Jan-2015, 16:24

Yeah Luis, I was asleep at the keyboard. 500 is awfully bright, though, you're right, definitely better for a monster enlarger, I think.

By the way, when using a light meter to measure EV values on the easel, and adjusting the bulb, how close do you aim for in terms of matching the values? I think I got within .4 EV. Brightest in the middle, I assume.

If my memory is right I think the Atlas bulbs get about .3EV with a 180mm lens at f/8, and with the ph/303 bulbs I got about .4EV. This is for 5x7 enlarged about 2X.

I have a few of the ph/303 bulbs I could probably be persuaded to sell.

However I'd probably build a simple LED setup, especially if you don't have a blower for the 500W bulbs already.

Looking at it you could build an LED replacement for about $100 and an hour of simple wiring and building. I've tested the CREE XT-E Cool white LEDs and they print very close to an incandescent bulb. And the Meanwell LPC 60-1050 power supply turns on and off instantly so it works well for enlarger applications (no issies with test strips).

StoneNYC

13-Jan-2015, 16:40

If my memory is right I think the Atlas bulbs get about .3EV with a 180mm lens at f/8, and with the ph/303 bulbs I got about .4EV. This is for 5x7 enlarged about 2X.

I have a few of the ph/303 bulbs I could probably be persuaded to sell.

However I'd probably build a simple LED setup, especially if you don't have a blower for the 500W bulbs already.

Looking at it you could build an LED replacement for about $100 and an hour of simple wiring and building. I've tested the CREE XT-E Cool white LEDs and they print very close to an incandescent bulb. And the Meanwell LPC 60-1050 power supply turns on and off instantly so it works well for enlarger applications (no issies with test strips).

I'm honestly still confused about the difference between all of these bulbs and the original Saltzman enarger bulb I own.

Jac@stafford.net

13-Jan-2015, 16:43

I would need the king neck ones I think for the Saltzman, hmm missed them too, I would pay $25 for a long neck one too hahaha.

If by King Neck you mean a longer neck, then you could hop over to a decent hardware store and get a ceramic socket extension for a couple dollars.

Tin Can

13-Jan-2015, 16:50

If by King Neck you mean a longer neck, then you could hop over to a decent hardware store and get a ceramic socket extension for a couple dollars.

Bulb OD and filament glow diameter are also considerations the ancients designed for.

Elwoods in particular need the right globe diameter, glow diameter, bulb position and the nearly 360 degree light to reflect off the focus dome.

I imagine point source condensers are also sensitive. Read my CB7 restoration comments elsewhere on this forum.

Larry Kellogg

13-Jan-2015, 20:40

If my memory is right I think the Atlas bulbs get about .3EV with a 180mm lens at f/8, and with the ph/303 bulbs I got about .4EV. This is for 5x7 enlarged about 2X.

I have a few of the ph/303 bulbs I could probably be persuaded to sell.

However I'd probably build a simple LED setup, especially if you don't have a blower for the 500W bulbs already.

Looking at it you could build an LED replacement for about $100 and an hour of simple wiring and building. I've tested the CREE XT-E Cool white LEDs and they print very close to an incandescent bulb. And the Meanwell LPC 60-1050 power supply turns on and off instantly so it works well for enlarger applications (no issies with test strips).

Larry,

You've done great work with your variable contrast LED solution for the Durst 138. Can any of us do that with an hour of simple wiring? It seems like it is more complicated than that. It would be great to somehow do a small production run of your solution.

I suppose I'll leave the 500w bulbs for people who need them more than I do. I trust that we'll always be able to figure out a way to make light.

Larry Gebhardt

13-Jan-2015, 21:05

Larry,

You've done great work with your variable contrast LED solution for the Durst 138. Can any of us do that with an hour of simple wiring? It seems like it is more complicated than that. It would be great to somehow do a small production run of your solution.

I suppose I'll leave the 500w bulbs for people who need them more than I do. I trust that we'll always be able to figure out a way to make light.

No, I'm not proposing anything nearly as complicated as the variable contrast head I built. Just a constant current power supply wired to an AC plug and a few LEDs mounted on 20mm "stars". If you get 4 stars with 3 LEDs each you will be able to get a huge amount of light out of an area about the size of the opening in the Durst head. Put a plexiglass diffuser in the heat absorbing glass carrier and you've got a very bright head that uses regular VC filters and works with any enlarger timer. Someone on APUG built a similar arrangement, but put it in an old Omega E diffusion head. I made one of those as my first LED project. It worked well, but the Omega got replaced with the Durst so I don't use it any more.

Maybe I'll build one and write up the instructions. It might make the extra Durst 138 I have more salable.

Larry Kellogg

14-Jan-2015, 01:37

No, I'm not proposing anything nearly as complicated as the variable contrast head I built. Just a constant current power supply wired to an AC plug and a few LEDs mounted on 20mm "stars". If you get 4 stars with 3 LEDs each you will be able to get a huge amount of light out of an area about the size of the opening in the Durst head. Put a plexiglass diffuser in the heat absorbing glass carrier and you've got a very bright head that uses regular VC filters and works with any enlarger timer. Someone on APUG built a similar arrangement, but put it in an old Omega E diffusion head. I made one of those as my first LED project. It worked well, but the Omega got replaced with the Durst so I don't use it any more.

Maybe I'll build one and write up the instructions. It might make the extra Durst 138 I have more salable.

Yeah, I figured, but I really want a variable contrast head with finer resolution than half grade increments. ;-) Is there any way we can get instructions and build one of those, or buy them from you?

Larry Gebhardt

14-Jan-2015, 07:14

Yeah, I figured, but I really want a variable contrast head with finer resolution than half grade increments. ;-) Is there any way we can get instructions and build one of those, or buy them from you?

My plan was to create a printed circuit board based on the prototype I built. However I've been using the prototype for two years and haven't finished the printed board design. I've had a few new ideas since the original design, so I'll see if I can get them integrated and the board designed and printed. Then I'll sell some of the blank boards at a low cost.

If you are willing to build a prototype board I can certainly provide some pictures and a description of what needs to be done. It's really not much, especially if you don't want it to switch AC for safelights. You need an Arduino, keypad, 20x4 display and some Buck Block drivers with a few transistors. All of it's pretty standard stuff in the Arduino universe.

I don't really want to get involved in turning this into a business. I'm mostly afraid of the liability of sending out electronics that use AC power (I don't want to fry someone). But I've found some new drivers that will boost a 12V DC power supply to higher voltage to drive the LEDs. So something could be built that uses a standard PC power supply, which would simplify things a lot.