Cold light head vs. diffusion head

Doug Bennett · Jan 14, 2005

I'm sure SchwinnParamount is now thoroughly confused :confused:

Condenser lenses collimate the light; that is, they get all the photons marching in a straight line. Diffusion enlargers send light through the negative at all different angles.

The Callier Effect, as I understand it, deals with light striking a medium, i.e. the negative, from a directional source. One would hope, with a properly exposed negative, that as density increases, the amount of light passing through the negative decreases proportionally. The Callier Effect says, though, that this relationship becomes skewed, and with particularly dense areas of a negative, proportionally very little light is passed through. So, your shadows get darker and darker, but you still don't show much highlight detail. Hence, "blown" highlights. No "glow." "Chalk and soot."

I don't know why light striking at multiple angles, as in a diffusion source, passes through the negative better than a directional source, but apparently it does.

That being said, Schwinn, museums are full of fine prints made on both types. It's really a matter of gearing your process to the equipment.

dancqu · Jan 14, 2005

Helen B said:
Um, strictly speaking... condenser lenses focus
the light onto/into the objective lens, not the negative.

That is true for one condition. The lens must be positioned so
that it is at the focal point of the condensers. If the lens be
racked up or down any amount than that is no longer true.

I think this to be the case. The lens must not be positioned
beyond the condenser focal length. I've a 105 on my Omega
B8 and have the long focal length condensers installed. At
full extension the lens is at or a small fraction of an inch
shy of the condenser's focal length. So, the lens falls
at or within the condenser focal length at all times.

I think it may have already been said, in effect, that smaller
formats may be printed with long focal length condensers
and a short focal length lens. If one wishes to tighten
that condenser beam for a brighter projection add a
supplementary lens; at least for many Omegas.

An easy test may be made. Let me know if interested. Dan

Helen B · Jan 15, 2005

'That is true for one condition. The lens must be positioned so
that it is at the focal point of the condensers. If the lens be
racked up or down any amount than that is no longer true.'

Often the lamp height can be adjusted easily and left in the position appropriate for the majority of the work you do. At least that's how I do it. How much tolerance there is depends a lot on the type of lamp (point, clear, opal).

'I think it may have already been said, in effect, that smaller
formats may be printed with long focal length condensers
and a short focal length lens.'

Maybe it's worth checking for even illumination at the working aperture if you have a mismatch - most of the time things will be OK though. Results seem to vary depending on the lenses and lamp in use.

I mentioned the Callier effect by posing rhetorical questions rather than launching into yet another of my irrelevant, confusing speeches. Maybe I should have said "Does it really exist in enlarging?" Ctein presented some thought-provoking evidence in two articles on the differences between diffusion and condenser heads in the Jan/Feb and March/April 1999 issues of PT.

Best,
Helen

SchwinnParamount · Jan 15, 2005

Doug Bennett said:
I'm sure SchwinnParamount is now thoroughly confused :confused:

Condenser lenses collimate the light; that is, they get all the photons marching in a straight line. Diffusion enlargers send light through the negative at all different angles.
...
. So, your shadows get darker and darker, but you still don't show much highlight detail. Hence, "blown" highlights. No "glow." "Chalk and soot."
...
That being said, Schwinn, museums are full of fine prints made on both types. It's really a matter of gearing your process to the equipment.

My eyes started glazing over until I read 'collimate' and my ears perked up. I know what that means from one of my physics classes at Berkeley so many years ago. Actually, your mention of 'chalk and soot' strikes a familiar chord here. I have too many negatives that I can't milk more than chalk and soot out of. Sounds like a diffusion light source is the way for me to go. I'll keep my condensors on the shelf and use them in the right situation.

I'm going to pick up the cold light head tomorrow (Aristo if memory serves) and let you all know what comes of it for my prints

rbarker · Jan 15, 2005

SchwinnParamount said:
. . . I'm going to pick up the cold light head tomorrow (Aristo if memory serves) and let you all know what comes of it for my prints

Aristo makes two types of cold-light heads - a single lamp for graded papers, and a dual tube unit for VC papers. So, if you use VC papers, be sure to get the right one. Also, look into compatible control and timer units. Because the light output can vary, the special timers often have light probes to sense the variations so it can adjust exposure time accordingly.

lee · Jan 15, 2005

Ralph is partly right. Aristo makes two types of lights the dual tube and a tube called a V54 which can be used with both graded and VC paper. Granted the graded paper is easily worked with the V54 as does the VCL 4500 but this head can be used more readily with the VC paper as the light output is more closely matched to the sensitivity of the VC paper. The older head is called the V45 and is much bluer and is used for graded paper. There is talk (not having done this) of using a 40ycc filter in the light with the V54 head to help warm the blue output of light. I dont know if this works or not. Maybe some of the other people would have a working knowledge of this.

Doug Bennett · Jan 15, 2005

I'd love to have the Beseler VC head that goes with my 23CII enlarger, or an Aristo head. Unfortunately, as the single wage earner in a family of 4 (with teenage drivers), my budget didn't permit it.

I inherited an Omega C760 enlarger with a dichroic head. The enlarger itself is rendered useless because the focus was driven by gum rubber wheels, which had long ago crumbled. Parts aren't available.

I've had the dichroic head cobbled onto the enlarger, but today's project is to fabricate a mounting plate. It will slide into the slot where the condensers were. If it goes well, maybe I'll post some pictures of the process. The C760 dichroic head seems to work well, and can be bought cheap. In recent auctions they sold for $20.00-50.00.

dr bob · Jan 15, 2005

SchwinnParamount said:
Does anybody know what the effects these two heads have on printing? Are they basically the same effect? Are they both better than using a condenser head?

As others have said they are different and one must make up their own minds. I find the condensers more work as the condenser surfaces must be cleaned et c. and the light source seems to be more critical.

Therefore I choose the condenser system! I know, you are all asking - "Do you always do everything the hard way?" so I will tell you:
Yes! Standing up, in a hammock, in a windstorm....

Seriously, I personally like the look I get with the condenser system on the landscape prints which I do most often. They seem to have just a slightly overall sharpness and "better"contrast (whatever that is). OBTW, the difference can be seen only on the print, not on a scanned image. I love a mystery.

Nick Zentena · Jan 15, 2005

Doug Bennett said:
I inherited an Omega C760 enlarger with a dichroic head. The enlarger itself is rendered useless because the focus was driven by gum rubber wheels, which had long ago crumbled. Parts aren't available.
.

Wasn't the 760 still being sold up to a few years ago? And parts aren't available?

Doug Bennett · Jan 15, 2005

Nick Zentena said:
Wasn't the 760 still being sold up to a few years ago? And parts aren't available?

Omega says parts are no longer available. There was a company in Canada that would rebuild the focus mechanism for $175.00, but I don't think it's worth it. I could probably machine something if I really wanted to.

This arrangement, with the C760 head on my Beseler, has promise. It's a 2-3 minute swap between condenser and diffusion, and the price was right.

Maine-iac · Jan 16, 2005

Tom Stanworth said:
Most agree that cold light and diffusers produce the same approx look and contrast. They reduce surface marks and imperfections on the neg. Cold cathodes are not normally OK with VC, tho some are specifically designed for it.

Actually, after I gave up my condensers and switched to an Aristo cold light (many moons and several technological generations ago), I was able to use it quite successfully with variable contrast paper, simply by inserting appropriate contrast filters between the negative carrier and the cold light unit. However, on the Beseler 45, this was inconvenient, so I eventually traded my cold light for a dichro colorhead, which I still use for split-filter, VC printing.

Larry

Peter Schrager · Jan 16, 2005

Diffusion VS....

Larry-just was curious if you see any difference in your prints with the dichro head? Personnaly I have both a V-54 lamp on a beseler and a Zone-VI VC head on an old Burke and James. I've been using the B+J alot more lately as it has a glass negative carrier and I have the perennial alignment problems with the beseler. Oh well.......that's analog I guess
Peter

Maine-iac · Jan 17, 2005

peters said:
Larry-just was curious if you see any difference in your prints with the dichro head? Personnaly I have both a V-54 lamp on a beseler and a Zone-VI VC head on an old Burke and James. I've been using the B+J alot more lately as it has a glass negative carrier and I have the perennial alignment problems with the beseler. Oh well.......that's analog I guess
Peter

No, I don't see any difference. The cold light was excellent, but the dichro colorhead is just much more convenient. Maybe I'm one of the lucky ones, but I haven't had any alignment problems with my Beseler 45. It's about 30 years old, and still cranks along. I print almost always at f11 with my Schneider Componon, and have not noticed any areas at any enlargment (though I've never printed larger than 16X20 and not often--mostly 11X14) that are not sharp due to alignment problems. And I'm pretty fanatical about sharpness, so I think I would have noticed. If there is an alignment problem then it's covered by the depth of field. However, when I printed Ilfochromes, I was often shooting the Schneider wide open or nearly so, and didn't notice any then, either.

Larry

ann · Jan 17, 2005

check with Harry at classic enlargers for omega parts, etc

Ronald Moravec · Jan 19, 2005

I hate to admit I have many enlargers for different type negs. A good neg that is not overly dense will print well on either with indistinguishable results, well perhaps a bit extra contrast in the shadows with the condenser.

A color diffusion head and cold light will make identical prints on the same grade of paper.

richardjx · Jan 25, 2005

Condensor vs diffusion heads

Hello

IMHO, cold light heads give smoother rendering of diffuse highlights, with more subtle variations of highlight details, as well as less contrast, less dust, less sharpness etc.

This has to do with the Callier Effect, where the transmission of light through the silver is not uniform with increasing density. Non-collimated light is not affected as much by the denser silver, for some reason I have yet to understand fully.

Check Fred Picker's book "Zone VI Workshop" for some A/B comparisons of the two types of light sources. (Saint)Ansel(mo) Adams used Cold Light heads for most of his later work.

Cheers

stinkjet · Mar 14, 2005

You're correct, dancqu....it will NOT work as a diffuser. Unless of course you don't mind a big, fat hot-spot in the middle of your prints.

stink

Cold light head vs. diffusion head

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