Cold lite?

johnnywalker · Feb 18, 2011

Adrian Twiss said:
I have been internally debating the idea of getting a condenser enlarger to supplement my Durst Laborator which has a VC diffuser head. After reading this it looks like my time would be better spent fine tuning my negatives to print with a diffusion light source.

From reading this thread I gather that a cold light head and a diffusion head are not exactly the same thing, and diffusion lights may not have the same issues my cold light head did. Not sure though.

Ken Nadvornick · Feb 18, 2011

Well, I realize that everyone's personal experiences are valid for them. But for the life of me I've just never seen all of these reported problems with fluorescent tube heads. My experience has always been one of reliable, rock-steady output with zero hand-holding on my part. But then that's the essence of closed-loop systems. They are by design intended to remove the need for hand-holding.

A typical darkroom session begins* by turning on an ancient Zone VI single-tube head (with an upgraded V54 lamp) and an equally ancient Zone VI Compensating Enlarging Timer. The head came with a photocell already installed. It mates to the timer. There is an internal heater that, in 20 minutes, has done its job. That frees me to set out chemistry, mount a negative, compose, focus, yadda, yadda.

From that point forward I never, ever have to think about the light source again - period. The photocell watches. The timer compensates. The seconds are adjusted on the fly. And the light is ungodly steady in its delivered volume. Changes in lamp tube temperature have no effect. Changes in focusing time, exposure time, down time... all of it, means nothing. All sources of drift are effectively factored out without any effort - or even thought - on my part.

When paired with a similar Zone VI Compensating Developing timer for my developing tray I can, as I said earlier, make identical prints, on the first try, a week apart. That's not hyperbole. I've done it. In fact, I once did it with step wedge prints while testing contrast filters. And if ever there would be a procedure that would show even a slight drift in the light source, that would be it.

To be perfectly honest, I'm so damned spoiled by the fact that I can completely factor out my cold light head as a variable that it would be like starting all over again if I had to worry about it at any level. Heck, if I ever have to go back to light bulbs and condensers you can be darned sure that the first thing I'll do is install a photocell into the bulb housing. Those guys are subject to drift as well, and color changes with it.

I've just never seen all the fiddling everyone says in endemic to these sources. But then my water temperature is also rock-steady (Hass Intellifaucet K250), and my magnetically-stirred hotplate solutions are - or can be, if I need them to be - rock-steady (Corning PC-420D with feedback temperature probe).

These are not Rube Goldberg solutions. Not a shred of chewing gum or duct tape to be found. Instead, they are elegantly designed and implemented solutions by people who knew what they were doing. They are fire-and-forget solutions. You simply turn 'em on and walk away with one less variable to worry about. Every single time...

Ken

* Or began, since I'm now still wrestling with rehabbing that used Aristo VC head that is about to get new tubes.

Ian Grant · Feb 18, 2011

johnnywalker said:
From reading this thread I gather that a cold light head and a diffusion head are not exactly the same thing, and diffusion lights may not have the same issues my cold light head did. Not sure though.

A cold cathode/cold light head uses a fluorescent tube, expensive because they are handmade but they have a long working life and generate very little heat, there's then a diffuser between it and the negative.

A VC diffuser head or colour head uses a Tungsten halide bulb or set of bulbs and a light mixing box to scramble the light, this also uses a diffuser at the bottom of the box just above the negative.

So in terms of output both give near identical scattering of light, a disadvantage of heads with Tungsten Halide lamps is extreme heat particularly if there's more than 1 lamp, a De Vere 5108 uses 4 500watt bulbs so needs two cooling fans, the lamps have a short life and are expensive.

The big advantage of a Colour/VC diffuser head is that dichroic filters can be placed between lamp & mixing box to control colour balance or VC filtration.

Ian

RalphLambrecht · Feb 18, 2011

johnnywalker said:
From reading this thread I gather that a cold light head and a diffusion head are not exactly the same thing, and diffusion lights may not have the same issues my cold light head did. Not sure though.

There are two types of density: specular and diffuse. The ratio of the two is called the Callier coefficient. No existing light source is truly specular or truly diffuse, but point-light sources are very close to being perfectly specular, and cold-light and diffusion heads are very close to being perfectly diffuse. A condenser head is somewhere in between. In other words, as far as the enlarging 'quality' of light sources goes, cold-light and diffusion heads are the same.

johnnywalker · Feb 18, 2011

The glass on my cold light head is a cyan colour. You can barely see the image on the paper when the filter is in place, the safe-lights on, and the lens at a middle f-stop. This makes focusing difficult (even wide open, and impossible if the red filter is in place) and it fools the enlarging meter as well as me. On the other hand, the paper is exposed very quickly (faster than the equivilent f-stop on the condenser head). Is this typical, or unique to the Taucoli head I have?

RalphLambrecht · Feb 18, 2011

All I can say is: photographic paper is very sensitive to blue light.

one example:
http://www.ilfordphoto.com/Webfiles/2006130200232336.pdf

That's why I always propose a yellow filter for paper negatives.

Reinhold · Feb 19, 2011

Re-read Ken Nadvornick's post # 27.

I've had the same set-up for 15+ years and can confirm that he speaketh the truth.

All this yodeling over light sources are other folks' problems, not mine...

Reinhold

www.classicBWphoto.com

Wade D · Feb 19, 2011

This has been an interesting read but the OP's question seems to have been answered in post#2.
Personally I have never used anything but condenser enlargers and taylor my negatives to match them. Some folks say my negatives look flat but that's what works for me.

RalphLambrecht · Feb 20, 2011

Sorry for hi-jacking the thread again.

David A. Goldfarb · Feb 20, 2011

I've owned a couple of cold light heads--a Graflarger back and an Aristo Hi-D head for my Omega D-II.

I do like the dust/pinhole suppression effect of a diffuse light source, and cold light does this well. This may also cause some reduction in sharpness, but I try to make up for that in other ways--glass neg carrier, apo lenses, checking alignment, negs developed to sufficient contrast of course.

I generally prefer graded papers, so the filtration issue isn't a big deal for me.

The Graflarger back was handy for working in a small space with a 4x5" camera as the enlarger on a copy stand, but the old-style light source had to warm up to give consistent output, and is unquestionably a pain to use for this reason, unless you're enlarging through a shuttered lens and can control exposure time that way, which is probably the original intended use of the Graflarger back, for the photojournalist on the road who might have print in a motel closet at night, englarging through the taking lens. It was good enough for newsprint. I keep it around for the day, perhaps, when I might be spending a year living abroad and might want to be able convert my camera temporarily into an enlarger.

The Aristo Hi-D head has a heater like most more modern cold light heads, which significantly improves the consistency, but I've added a Metrolux compensating timer, and this combination is really excellent, particularly when I've had to make prints in quantity, because the light output is high, and the Metrolux gives absolute consistency, even for very short exposures timed to a precision of 1/10 sec.

This is great for tasks like printing a stack of 50 postcards from a medium format or 4x5" neg, where the exposure time might be something like 2.3 sec. I remember trying this once with the Graflarger head, of course exposing them all after making a couple of test prints, then taking them over to the developer tray and realizing that somewhere around 20 prints in, they were too dark. The Metrolux solves this problem.

A compensating timer is an expense, but for the way I work, I like the combination of cold light and compensating timer.

Steve Smith · Feb 20, 2011

RalphLambrecht said:
This is probably the only questionable statement in any of the AA books. Not too surprisingly, because AA did not use a cold light head himself, otherwise, I'm sure he would have noticed.

On page 28 of The Print (14th edition) is a picture of AA's cold light source which fitted in the space in front of his 36 bulb light source. This is mentioned in the text:

"I have since replaced this unit with a powerful cold light system which greatly reduces exposure times....."

The caption to the picture suggests that the shorter exposure times are due to the blue cast of the light.

So I think he did use it, at least for a while.

Steve.

RalphLambrecht · Feb 20, 2011

Thanks for the correction, Steve.

When I was in AA's darkroom, after his death, this cold-light grid was not present, and John Sexton explained to me how AA loved this array of bulbs, because he was able to individually turn bulbs on and off to give emphasize to certain areas of the print. This cut down on dodging and burning in some cases. I'll check with John if and for how long AA had used this cold-light grid and report back.

Steve Smith · Feb 20, 2011

That 36 bulb back does look good though and I like the idea of selectively switching to give some control to intensity in selected areas.

Steve.

Mainecoonmaniac · Feb 20, 2011

I could only speak for myself, but I use a dichroic color head and it works well for me. I've used cold light heads while working for a university photo lab and find them hard to use with vc paper. I wonder if they're designed for blue sensitive graded paper? I've heard that some printers that use cold light heads have circles in their prints due to the tubes in the head.

RalphLambrecht · Feb 20, 2011

Just to be clear, I'm not knocking cold-light enlargers. I truly believe that perfect prints can be made with any type of enlarging head (maybe with the exception of point-light sources). I was only interested in understanding why folks would put up with, what I thought to be, the challenges of a cold-light head when they can get the same benefits from a 'simple' diffusion head.

What I learned from this thread is that they are not as cumbersome as I thought (anymore) and that they do have some benefits that I did not consider (speed).

Thanks for the replies and sorry for hi-jacking the thread again.

Wade D · Feb 20, 2011

RalphLambrecht said:
Sorry for hi-jacking the thread again.

I did not mean to sound as if I was picking on you or anyone else for the length of the thread. It has been very informative to someone like me who has never tried anything but condensers. Would a piece of opal glass above my condensers qualify as a diffusion source? It would be interesting to try it out.

Ken Nadvornick · Feb 20, 2011

Wade D said:
Would a piece of opal glass above my condensers qualify as a diffusion source? It would be interesting to try it out.

I've heard in the past of people doing this. I've never tried it, so I can't say one way or the other. But it would seem to pass the common sense test if the collimated light above it was evenly distributed.

Maybe when Ralph reads this he could weigh in?

Ken

Ian Grant · Feb 21, 2011

Ken Nadvornick said:
I've heard in the past of people doing this. I've never tried it, so I can't say one way or the other. But it would seem to pass the common sense test if the collimated light above it was evenly distributed.

Maybe when Ralph reads this he could weigh in?

Ken

My first enlarger, an early Gnome, has a piece of ground glass above it's single condenser, it used a plain 12v bulb (and a transformer) so diffusion was necessary. for even lighting.

Most modern condenser enlargers use coated bulbs that give out very diffuse light anyway so adding an additional diffuser would be of little benefit.

Ian

Ken Nadvornick · Feb 21, 2011

Oops. I misread...

I thought you guys were saying opal or diffusing glass below the condenser lenses. In other words, the same location directly above the negative that cold lights use it. But you are saying above the condenser lenses. Sort of like a very large bulb surface feeding the condensers.

I have heard of people placing diffusion material below, but not above. Interesting.

Ken

RalphLambrecht · Feb 21, 2011

Ian Grant said:
... Most modern condenser enlargers use coated bulbs that give out very diffuse light anyway so adding an additional diffuser would be of little benefit. ...

I agree. It won't help much but cuts down on the light.

Ronald Moravec · Feb 21, 2011

I used to wade thru this years back, so i did some of my tests. Condenser with frosted bulb. Same with added diffuser. Aristo head with heater, first with standard blue tube, later with V54, color head.

Prints are much the same IF YOU MAKE THE NEG FIT THE SOURCE. Prints are not the same if you print on 2 paper with condenser and 3 with diffusion. With taylored negs, condensers give more contrast in the shadows, diffusion give more detail in highlights. The effect is very slight and you really need to place them side by side to see it. There is no way you could look at one or the other alone and pick enlarger.

If burning in highlights is important, diffusion is much easier EVEN IF the neg is made for condenser.
Color heads work the same as cold light.

Dust suppression is very minimal if it exists at all. I do have one neg that got a scratch from the cut end of the 35 mm roll. One of my best shots. The scratch prints on a single condenser and disappears on diffusion. It also needs some highlight burn. I print it on a diffusion.
Grain reduction is there, but minimal. Again taylored negs side by side from 35 mm to see it. Dust is too big to suppress period.

V54 tube is the only one worth using for VC. Color heads works perfectly.

Adding diffusion under the bulb of a condenser and above the condensers lower the contrast 1/2 grade putting it between condenser and diffusion. Eats a lot of light.

My take on the whole thing from tests in my darkroom done by me, Focomat 1C and V35 and also 4x5 on D2 ( condensers and Aristo) and D6 with color head. There is but 1/2 to 2/3 grade difference on focomats. 4x5 is a full grade difference.

RalphLambrecht · Feb 21, 2011

Ronald Moravec;1142193... Prints are much the same IF YOU MAKE THE NEG FIT THE SOURCE. Prints are not the same if you print on 2 paper with condenser and 3 with diffusion. With taylored negs said:
Prints are much the same if you adjust the negative contrast to fit the light source.
Prints are much the same if you adjust the paper contrast to fit the light source.

The difference between condenser and diffuser is not necessarily one grade. Actually, the difference between grade-2 and grade-3 paper is not necessarily one grade.

Almost identical prints can be made from both enlargers by adjusting negative or paper contrast or both. Any remaining difference is due to the interaction of paper and negative characteristics curves and not the the light sources, that's why deviating burn-in behavior cannot be credited to the light source IMHO.

Ronald Moravec · Feb 22, 2011

Your results are your results and I would tell you to reread what I posted. I specifically said single condenser Focomats and diffusion Focomat differ by 1/2 grade. Omegas double condenser and diffusion color head differ by 1 full grade.

Prints do not look the same by changing printing paper and light sources at least in my darkroom. If you are pleased, then that is what counts. Changing grades just does not do it for me.

RalphLambrecht · Feb 22, 2011

Ron

No controversy intended, just curiosity.
Changing paper grade, however, should create a reasonable match between two print from negatives with different gradient within reason. I wonder why you have a different experience.

How do you change paper grades?
How do you know what paper grade you need for the match?
How do you know what paper grade you are getting from your system?

Cold lite?

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