Converting condenser head to "cold light head" via flashed opal glass difusion

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" negatives, I am in the middle of converting my Omega D5 condenser head into a diffusion source in the following manner:

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I am placing a piece of diffusion material (flashed opal glass precisely measured, 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 from 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).

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

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.

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

Andre,

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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.

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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.

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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.

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

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.

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Regards,

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Doug.

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

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.

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.

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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.

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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.

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A dichroic color head also works extremely well if you cannot find

a "cold light" head.

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.

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.

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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

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PS: Should anyone out there try this conversion too, I assume no

liabilty should your darkroom go up like a dry Christmas tree :>)

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?

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)

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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 :>)

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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.

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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

PS: Dave, Sorry I didn't answer the Aristo cold light head portion of

your question. Andre

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.

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Happy New Year,

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.)

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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

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.)

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

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.

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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).

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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.

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.

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What's up? and thanks...

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.

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If there's any diffusion effect, it's probably mostly from light

scattering at the edges of the grooves.

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