View Full Version : Converting condenser head to"cold light head" via flashed opal glass difusion

Andre Noble
28-Dec-2000, 21:06
Finally inspired by a recent post re: Cold Light v. Condenser and over-perspired from trying to burn in runaway highlights in too prints from "contrasty" negati ves, I am in the middle of converting my Omega D5 condenser head into a diffusio n source in the following manner:

I am placing a piece of diffusion material (flashed opal glass precisely measure d, cut round) in the bottom most part of the condenser assembly, so that it will be situated closest to the negative carrier. Then, because of the light loss f rom the diffusion, I am replacing the standard 75 watt bulb with a more powerful one (a 250 watt for starters, if this runs too hot, then 150 watt).

I am interested in hearing from experienced B&W printers who have made similar c onversions on your experience with it. How did you like the results vs. origina l set up, any drawbacks or other details to be concerned about, etc. Thanks. A ndre Noble

neil poulsen
29-Dec-2000, 03:17
You can always give it a try. I did, but with dismal results. There wasn't nearly enough light with which to print. Perhaps the higher wattage bulb will help, but I wonder.

Andre Noble
29-Dec-2000, 07:53
Neil, could you tell me what type of material were you using for diffusion, and where did you place it along the light path? Andre

Sergio Ortega
29-Dec-2000, 09:36

Before anyone gets carried away with this "conversion", be advised it will not work. And it might even set your enlarger on fire if you use the same tranluscent, plexiglass diffusion material found on most real cold light sources.

What makes a cold light a "diffusion light source" is not the diffusion disc/panel located immediately below the light tube grid. I suggest you research more closely what type of light sources cold lights use, the differences between condensor and cold light sources, and also study their designs very carefully.

Before anyone embarks on a similar project, check out Aristo Grid Lamp Products' web site for a clear, concise description of cold lights, what they do, how they're designed (there are some interesting diagrams comparing the two light sources) and their benefits over simple tungsten bulb light sources.

They can be found at: www.aristogrid.com. Good luck, Sergio.

Doug Paramore
29-Dec-2000, 10:22
Andre: I tried to do the same thing about 10 years ago without success. While I was able to diffuse the light a bit, when I got enough diffusion to make a difference in the way the highlights were printed the light was too dim. I was able to find a used cold light head at Midwest Photo Exchange. The Aristo cold lights are not really that expensive brand new. Maybe someone on this great web site has one for sale (I don't). I printed a neg that took considerable burning in of a bright area and printed it with the condenser and diffusion disc. When I got the cold light, it printed with little or no burning in of the same area, and the print was much more brilliant. Spend the money for a cold light head, even if you have to save up for a couple of weeks or so. It really does make a difference in your prints.



Andre Noble
29-Dec-2000, 12:21
Sergio, I saw the idea from a man known as the "Photo Dr. " from the Photo-Net website medium format forum. He stated he used this precise conversion of his condenser to approximate cold light diffusion with success for many years with his Omega D2, and the results approximated cold light diffusion close to 1/2 stop identical results - I presume he was using normal square (graded) filters in the condenser lamp house. He didn't mention any thing about a fire. (Although his prolific, well researched postings mysteriously stopped near the end of 1999)??? Andre

Frederick Leif
29-Dec-2000, 13:07
I haven't attempted that conversion, having installed an Aristo source in my Besler. However, I would hesitate to increase bulb wattage beyond that recommended by the manufacturer. A 250 watt bulb would generate a lot of heat in the lamp housing and lamp socket, and draw a higher current through the wiring. At least check that the components are rating by UL for the service you're attempting.

Ellis Vener
29-Dec-2000, 14:29
Years ago I tried this too on an Omega D2. I tried opal glass on of, below and in place of the condensors. I also tried using rosco Tough Spun (a diffusion material designed for "hot lights" used for movie and still photography, again on top of and below and both below and abovethe condensors. None of these methods worked, the system just wasn't designed to give even light all the way across the negative and I always ended up with fall off, sometimes in unexpected places.

The heat build up was also increwdible, even with the same wattage bulb as the enlarger was designed with. I reinforce the other poster's warnings about putting in a higher wattage bulb.

I suggest you use a real diffusion head. Many used ones are availible on the market in different stores as well on e-bay and in the photo.net classifieds.

A dichroic color head also works extremely well if you cannot find a "cold light" head.

Brian Ellis
29-Dec-2000, 16:49
Andre - If the other answers aren't enough to discourage you, I'd suggest that your "run away highlights" aren't going to be cured by a diffusion light source or even by a true cold light source for that matter. It sounds as though you're just making negatives that have a density range that is excessive for a condenser enlarger. I'd suggest reducing your development time by 20% - 30% and see what that does to your highlights before making any modifications to your enlarger, paricularly when so many seemingly knowledgeable people don't seem to think it's a good idea.

Andre Noble
29-Dec-2000, 19:21
Dear Brian, Doug, et.al.: I just wanted to report back my initial results of a print I made with this cold light conversion set-up I put together this morning. I have the day off from work as a teacher, so while receiving wise advice to avoid the whole mess altogeher , I instead drove around LA, buying a piece of flashed white diffuse opal glass cut precisely to fit inside the condenser, and also a 250 watt GE enlarger bulb from Freestyle Camera. Total cost: $35. I then put the whole thing together and made an 8x10 print of a fairly-well contrasted 4x5 negative which previously gave me fits (not unlike many other negatives I shot). The initial results I find in the difference of the print diffused vs. Condenser set up is STUNNING!!! - This is my first experience printing B&W with a diffused light source. Regarding the print: First, I don't see anywhere on this print where I need to do spotting - a first! Second, shadows are open, just as they were in original scene, whereas with condenser print, they're unrealistically dark, murky. Sky has a uniform glow in difusion print, whereas in condenser print I usually find it lands either too dark or too light compared with the main subject. (Yes, my knowledge and use of filters for B&W film should be improved upon - and hence rendering of sky tone better). Highlights landed on the paper on test print instead of just remaining a dream. Diffusion print made with #1 filter, condenser print with #00 (and even then, I still had trouble placing higlights - and yes, I know I should have reduced dev 30% with this negative to begin with). To sum up: I think I'm on the right track. Printing with my condenser is just not as rewarding as I intuitively feel many of you more experienced printers feel about your dichroic or cold light printing.

Now it's off to Frye's Electronics for a mini fan to draw heat away from the condenser head, and then a hardware store for insulation for the power cord to protect it from the heat of the head as well. Expected total cost for my "cold light" conversion:$50.00. Andre

PS: Should anyone out there try this conversion too, I assume no liabilty should your darkroom go up like a dry Christmas tree :>)

neil poulsen
29-Dec-2000, 20:49
I used frosted glass that I purchased at a local glass store. neil

Dave Schneidr
30-Dec-2000, 01:24
Please keep us posted on the results of your opal glass experience. were printing times significantly longer? I was thinking of trying the same thing with my D5, going with a 150 watt bulb instead of the 75 watt I use now. I have come close to a cold light head. Can you proponents of cold lights tell me where you put the contrast filters when using the standard (non variable contrast) Aristo head? Do you set them right on top of the negative carrier or do you go to a below the lens filter?

Andre Noble
30-Dec-2000, 05:47
Dear Dave: on the top left and right sides of your Omega D5 condenser head you should see two rectangular plastic protrusions, each secured with 4 Philips screws. I unscrewed all 8 screws and took both of these plastic pieces off. Now there is more potential for cooling air flow around the bulb housing. Next I attached a tiny "Socket- 7" computer CPU cooler fan to it by passing one of those 8 screws through a screw hole provided on the fan, securely fastening it to the bulb housing screw receptacle (admittedly, I did have to saw off appx. 1/4 of the cooling fan's fins on this $12 fan in order for the whole thing to nestle deep inside the open space you will find once you remove these plastic pieces)

For power, I spliced the fan's power wires into those of an inexpensive 12 volt DC adapter, and then plugged the whole thing into the same electrical socket on my darkroom timer that controls the safelight. So now, after each print exposure, the cooling fan comes on, blowing cool air through and around the bulb assembly and out then other (open) side - when there, I noticed the air becomes noticeably less cool :>)

The reason I mention all this is because I don't believe the 150 watt bulb will be bright enough once you've introduced the flashed opal glass, so therefore I tried the 250 watt right off. And as other posters have noted, the 250 puts out HEAT. The 250 is certainly bright enough, at least with an 8x10 print from 4x5 negative, but like I said, even then the basic exposure was 30 seconds wide open at f5.6!! (The 150 enlarging lens is supposed to be near it's best at f5.6 anyhow) Nevertheless, I can't keep my eyes off the first print I just made today with this rig. I nailed this impossible negative after 4 prints and it's gorgeous!!!. It's a definite improvement over bare condensers.

Now, my remaining concerns are how the thing will work out with larger prints (ie, evenness of light across the print, possible excess exposure times, etc, - and for that I will keep you posted. Andre

Andre Noble
30-Dec-2000, 05:59
PS: Dave, Sorry I didn't answer the Aristo cold light head portion of your question. Andre

Doug Paramore
30-Dec-2000, 11:51
Andre: Glad you went ahead and tried the diffusion. As you are finding out, diffusion is the way to go. I was afraid to use a larger bulb with my enlarger, and didn't have the brains to install a cooling fan as you did. If you love the diffusion enlarger, wait till you try cold light...you will really get your mind blown. In the meantime, enjoy printing with your conversion. It really does make a difference.

Happy New Year,

Andre Noble
30-Dec-2000, 12:54
For any future readers of this post who have the time, motivation, and the appx. $55 to do this conversion, there are two important details I would be negligent not to mention: With the Omega D5, D2, etc. type condenser you must use 1/8" thick, circular (6.5 inch diameter exactly) - and not thicker- flashed opal difussion glass. With any thicker glass size, you will not have enough clearance in the condenser assembly to put the condensers back on the head once you've inserted the flashed opal. (And oh yeah, milky portion of glass goes at the very closest to the negative.)

Finally, I can remember times in the past while printing with the weak 75 watt bulb, whereby in the process of developing prints in another room and answering the phone, I forgot and left the enlarger on and consequently managed to have the enlarger bulb burning for an hour or more :( If that happened with the 250 watt, unattended, there'd be some price to pay. For safety sake, with the 250, I would suggest setting it up so that there's no way it can be accidently left in the ON position indefinitely in your absense. If your enlarger's bulb is powered through your timer - great. Then just be sure to find a way to disable the "focus" function (which allows your light to remain ON indefinitely). I disabled mine on my Beseler Electronic Enlarger timer by taping a 35mm film canister over the "focus" button to shield it from intentional (or otherwise) activation. Now, the bulb can only be turned on and left on via timer - with the max possible unattended exposure duration being only 99 seconds. Andre

John H. Henderson
2-Jan-2001, 09:43
Putting a fan in the head is all fine and dandy, but I'm more concerned about the ability of the wiring to handle the increased current. Going from 75W to 250W, you've increased the current draw 3.3 times, from 0.625 amperes to over 2 amperes. (Assuming US 120V RMS supply.)

james mickelson
2-Jan-2001, 19:56
The wiring will take a 500 watt bulb on the besselar enlargers. I regularly used a 250 watt bulb in my 45m. But you need to dissipate the heat. It will kill the enlarger really quick as well as the neg you put into it. James

Andre Noble
3-Jan-2001, 03:08
Using similar testing ideas from the chapter "Condenser vs. Diffusion Light Sources" in Ctein's book, "Post Exposure", this weekend I made some preliminary tests and findings regarding the illumination uniformity on the setup described above. I am happy to report that it produces a very uniform illumination using a 50mm enlarging lens across the 35mm negative carrier opening, with one important caveat: In the Omega 4x5 condenser head, the 3rd (variable) condenser - which is typically positioned in accordance with the enlarging lens used - must be removed entirely, just as you would do when printing with the 150mm lens. On the other hand, positioning the variable condenser in the conventional position (as one would with condenser illumination, at the bottom most slot) did result in significantly reduced print exposure times, but unfortunately, at the expense of the illumination eveness. There was a very mild, but noticeable circular hot spot ring in the middle of the test print.

I strongly suspect I will find the same result when I have a chance to test the set up with the 4x5 carrier and the 150mm lens. In fact, what struck me most when I first tried the thing was how the quality of the illumination from the from the flashed opal resembled that from a cold light head (save for the color temp difference of the light, obviously).

Finally, I had the privilege? of pulling out some extremely stubborn negatives which I wrestled with for MINUTES of burning time per print. (Picture I took in my youth of scantily clad models - it was a labor of love you might say) Between multiple 1 minute exposures, I simply let the cooling fan kick in and do it's thing. A "normally exposed and rationally processed" 35mm negative will need appx. 20- 25 minute exposure at f4. to make a properly exposed full frame print. My guess is that this is appx 3 times more exposure time than with the condensers and with 75 watt bulb.

5-Jan-2001, 16:00
Okay I have a related question... I tried the opal glass route with a hopped up bulb and it was too hot and I didn't feel like attaching an air conditioner to it so I began trying anything with less opacity as a diffusor. Ordered crap from rosco, tried tissue paper, frosting my own glass..everything I could think of... and then I stumbled across a plastic sheet magnifier(fresnel) and thought I'll try it and if it throws circles all over my photos then I'll call it "art" ... it worked with only 1 stop loss with a 75 watter. I guess because the focal length of the fresnel magnifier is about 12 inches and since the magnifier is only four inches away from the source and lens and turned upside down it diffuses rather than resolves.

What's up? and thanks...

Bill C
5-Jan-2001, 21:47
Trib, when you put the fresnel lens in, you just converted back to a condenser enlarger again. Probably the reason you lost a stop is because the condenser lens (fresnel) is not matched as well as the factory condenser. Good chance you would get the missing stop back by adding on another identical fresnel and centering them (ie, make sure they project the bright spot thru the enlarging lens aperture.

If there's any diffusion effect, it's probably mostly from light scattering at the edges of the grooves.

N Dhananjay
6-Jan-2001, 02:59
Dunno... It is also possible that the fresnel is basically taking the collimated light coming out of the condensors and directing it towards the edges (exactly, the way it does with a ground glass). In other words, it is un-collimating the light and making it diffuse. Just a thought. DJ