Advantages of cold light heads

jerry lebens · Apr 24, 2010

Sorry Sparky, I have to agree with Ralph regarding sharpness - diffusion enlargers are visibly less sharp. You can even make a condenser enlarger 'sharper' by reducing the diameter of the light source ; indeed, this is the theory behind 'point source' enlargers.

Anyone who's attempted to print with a point source will confirm the sharpness of rendition. I experimented with a Durst 184 set up as a point source and the graphic effect was electrifying. But I had to give up on it in the end. It was extremely labour intensive, trying to limit the, frighteningly intense, rendition of dust, scratches and watermarks etc...

Regards
Jerry

Sparky · Apr 24, 2010

Maybe I didn't get the point across clearly enough ralph- just trying to say that cold light and diffusion enlarger both share the characteristic - due to distribution pattern of the light source. I was trying to suggest that it wasn't some mysterious innate property of the cold light grid that causes this. Just trying to be clear. I felt that people reading the thread might not get that point. But apparently I wasn't even clear enough despite trying to be very clear in my language!

I was also trying to state that they are a more 'efficient' form of lighting to expose paper. Much more of the energy going into them acts on the silver - hence the 'actinic content' of the light.

RalphLambrecht said:
Sorry, but I can't follow your argument.

True, but 'apparently less sharp' is 'less sharp' to the observer.

True again, because they are both diffusion heads, but they are both 'apparently less sharp' than condenser heads.

Not if you compare cold light to condensers.

If you compare cold lights to other diffusers, such as a color enlarger, they offer little benefit (less heat) but have some major disadvantages (unstable light output, warm up time required) and usually cost more, at least if you figure in the electronics to compensate for some of the problems.

I find color heads simpler to use with less things to worry about. Cold lights produce excellent results, but there is an easier way to get there.

Sparky · Apr 24, 2010

jerry lebens said:
Sorry Sparky, I have to agree with Ralph regarding sharpness - diffusion enlargers are visibly less sharp. /QUOTE]

Yes - that's precisely what I am trying to suggest, Jerry. I agree too. And this was the exact point I was trying to make. A simple clarification. I probably got a bit too 'complicated' though.

Although I suppose I look at condensers not so much as being 'sharper' as simply being 'exaggerated' in their 'micro contrast'. Kind of like using a sharpness mask - where you have diffraction effects around each silver grain.

Q.G. · Apr 24, 2010

That ("exaggerated") would really be turning things upside down.
It's the diffuse (whether cold cathode or other) lighting that reduces things.

And it does so almost too much for comfort: those dust particles or scratches are no exaggeration. Very real. Yet they tend to disappear automagically when using a diffuse light source.
When that can happen to dust and scratches, things you don't mind disappearing, it can happen to image content too.

And given that we are dealing with a visual medium, that thing about apparent equaling real is correct.

jeffreyg · Apr 24, 2010

I have no science to backup my response but I was pleased with my prints when I used a condenser and also pleased when I switched to a cold light. I then switched to an Aristo grid 4500CL and find that easy contrast control and the savings on paper is appreciated. I don't print color but if so I agree with Ralph. With a good negative you can make a good print regardless of the light source. I've made some lovely pt/pd prints with sunlight and have seen LF prints that were exposed with a regular light bulb - they were exquisite. It boils down to what works best in your hands IMHO.

BetterSense · Apr 24, 2010

Well I already packed away my condensers, but with the division in this thread, now I'm obligated to make a print both with and without the cold light for comparison. Or maybe if I just like the results from the cold light I will just keep using it.

RalphLambrecht · Apr 24, 2010

BetterSense said:
Well I already packed away my condensers, but with the division in this thread, now I'm obligated to make a print both with and without the cold light for comparison. Or maybe if I just like the results from the cold light I will just keep using it.

That will be tough. To truly compare, you'll need two different negatives, one developed for the diffuser and one for the condenser.

I've done it, but it took a while to get the two negative contrasts just right.

ic-racer · Apr 25, 2010

RalphLambrecht said:
You seem to have this under control, but I'm glad I don't have to worry about it with my color head. I enjoy the stable light output (controlled by a voltage stabilizer) and wouldn't want to put up with the variables of a cold light. It looks to me that the cure is worse than the problem.

I don't want to bad-mouth that Aristo (because I may want to sell it some day ) But since making that graph I have converted over to the CLS2000 head on the 8x10. So now I also have voltage regulated quartz halogen/dichroic light sources on all 4 of my enlargers.

In my opinion (and probably Ralph's also) these dichoric heads are the Gold-standard. With today's market, there is no need to futz around with cheaper cold-cathode or LED light sources when dichroic heads can be purchased so cheap these days.

For example when my Durst sold new in 1988 the CLS2000 head alone was about $15,000. The original buyers had the Durst chassis delivered, instead, with the Aristo 1414 head at $600 from the USA distributor (per the original invoice). It was a cheaper alternative that did not perform as well.

RalphLambrecht · Apr 25, 2010

I think dichroic heads are unbeatably good, but I wouldn't mind trying a three-color LED light source one day.

Sparky · Apr 25, 2010

Q.G. said:
That ("exaggerated") would really be turning things upside down.
It's the diffuse (whether cold cathode or other) lighting that reduces things.

And it does so almost too much for comfort: those dust particles or scratches are no exaggeration. Very real. Yet they tend to disappear automagically when using a diffuse light source.
When that can happen to dust and scratches, things you don't mind disappearing, it can happen to image content too.

And given that we are dealing with a visual medium, that thing about apparent equaling real is correct.

QG - please read what I said - it's all relative. For ME (i.e. - Myself, the person I call "I", the son of my mother, etc etc...) - I PERSONALLY find them exaggerated.

I really cannot speak to your experiences - but I have never had any but stunningly, razor's-edge sharp sharp sharp from a cold light. Both apparently and absolutely. It easily bears inspection under microscope.

But the terms you speak in are relentlessly subjective. I just hope you understand that. None of us disagree that you see an apparently higher contrast and apparently higher degree of sharpness (which I reserve the right to call 'exaggerated') at a certain viewing distance. I agree. I see the effect too. Anyone in their right mind does. Nobody's disputing that. Everyone loves you.

archer · Apr 26, 2010

Perception vs Fact

I photographed a pair of eyes in 1964 and enlarged the image to 30in X24in. I used a condenser enlarger and an Ektar enlarger lens. I'm submitting a copy of full size crop from that print. I have printed the image many times with a diffuse light source and while the resolution may be the same, no print from the diffuse light source gives the same impression of sharpness as the condenser light source enlargement. The image was taken in 35mm, Panotomic X with an Exacta VXIIA and 50mm Pancolor lens at f16. Development was in Microdol X 1+3. Sometimes, perception is greater than fact.
Denise Libby

BetterSense · Apr 26, 2010

I printed my first time with the cold light head last night. Exposure times were similar to the 200W bulb in the condenser head. I actually did not notice a need to increase contrast on the paper...I printed a negative I have printed before and I had to use grade 1 and while I don't remember what I used before, it was surely not lower than grade 1. The picture looks fine, but the image on the baseboard sure looks blue!

Nicholas Lindan · Apr 26, 2010

Diffuse light sources can result in higher film speeds.

The logic goes that one has to N-1 the film (over expose/under develop) to reduce the contrast when printing with a condenser head so results are the same as with a diffuse head. Dr. Richard Henry estimates that Tri-X needs to be exposed at EI 200 or so to produce diffusion-like results with a condenser head. If this is done, though, shadow detail should be superior when printing with condensers.

Vice-Versa, if one exposes at box speed for a condenser enlarger one can N+1 the film (increasing the contrast) so that the diffusion enlarger produces the same contrast, thus raising the speed of Tri-X to 800. Shadow detail will be worse with the diffusion source.

If both films are exposed and developed identically then the condenser enlarger needs one grade softer paper / diffusion needs one grade harder. If printing with VC paper the HD curves get less well behaved at lower contrast filtration.

* * *

Historically, cold light heads were the low-cost alternative to condenser heads. I think they still are cheaper than a good condenser head (though it is hard to get a current list price for an Aristo head). As an offset to their lower cost, early cold-light heads had severe problems with repeatability when compared to condenser sources. With the availability of quartz-halogen diffusion heads there really is no reason to bother with a cold-light head. There are quite a few diffusion/quartz enlargers without filtration for the 35mm and MF markets. I think LPL makes a quartz-halogen diffusion enlarger for 4x5.

BetterSense · Apr 26, 2010

That's why I'm hesitant to start developing my negatives for the cold light head. If I have to use grade 3 a lot, then that's fine with me; I would rather that than have to print with a grade 0 when I use my condenser head.

Q.G. · Apr 26, 2010

Sparky said:
QG - please read what I said - it's all relative. For ME (i.e. - Myself, the person I call "I", the son of my mother, etc etc...) - I PERSONALLY find them exaggerated.

Yes, Sparky.
And I think YOU (the son of your mother, and all that) are turning things upside down.
Something wrong with that?

Sparky · Apr 28, 2010

Q.G. said:
Yes, Sparky.
And I think YOU (the son of your mother, and all that) are turning things upside down.
Something wrong with that?

Depends on which side of the mirror you stand on I guess...? (shrug)
I had the feeling we were talking from opposite sides of the same coin. I was just saying that as a 'diffusion light source kind of guy' that 'to me' condenser sources seem 'exagerrated' and so it's perfectly fair to say 'as a condenser kind of guy' that diffuse light sources seem too low in contrast. I see no conflicts here.

Bill Burk · Apr 28, 2010

I flipped through the Fred Picker Zone VI newsletters to see if he said anything specifically about diffuse color heads vs. diffuse cold light and couldn't find any mention. I think he might have approved if the technology was accessible in the late 70's / early 80's (and if he weren't so closely involved in the perfection of his own product.)

It's obvious he was adamant against condensers. He belittled a reviewer who took his cold light head as a gift and in his review mentioned he couldn't tell the difference between the two. Fred expressed his opinion as a statement of fact: The Callier effect, he said, is not a theory it is an effect.

Fred echoed Ansel Adams' opinion that highlights with condensers turn to chalk. Fred looked for highlights of cream.

Fred showed a graph of light output vs time unstabilized (like an oscilloscope trace of a square wave with slightly sawtooth tops showing the light output starts bright then dims progressively over time) vs stabilized (like a square wave). For a technician producing series' of prints and demanding repeatability this would be a very strong selling point for the Zone VI stabilized head.

I would find it impossible to switch away from one of his stabilized heads if I had one. It's hard to resist wanting one of everything Zone VI after reading the newsletters. (I personally use a D2 cold light head, unstabilized, without a dry-down timer - and I know I have to have one of those Zone VI setups one of these days).

Bill Burk · Apr 28, 2010

I wanted to add that Fred Picker worked primarily in 4x5. I can't think of a specific quote but I get the impression he didn't worry about enhancing sharpness.

In "The Fine Print," he gave one example, "Pemaquid, Maine" (looks like a small vein of quartz on a background of volcanic rock) where a condenser head helped by keeping a highlight open as he printed down the dark gray to near black.

Q.G. · Apr 28, 2010

Sparky said:
Depends on which side of the mirror you stand on I guess...? (shrug) [...] I see no conflicts here.

I do. As Bill wrote, the Callier effect is not a theory.

Contrast is actually, physically, lowered in one case, while nothing happens to it in the other case.

But i agree: as far as what expressing what you like best is concerned, the word "exaggerated" is merely ill chosen.

RalphLambrecht · Apr 28, 2010

Bill Burk said:
...Fred echoed Ansel Adams' opinion that highlights with condensers turn to chalk...

As far as I know, it was Fred who persuaded Ansel Adams to say this, and it's the only AA statement in his books deserving critique. It's simply not true, unless the negative was developed for a diffusion head. But then again, Ansel's negatives were developed for his self-made tungsten 'diffusion head', and they would not print well with a condenser. That may be the reason for his statement.

Bill Burk · Apr 28, 2010

RalphLambrecht said:
As far as I know, it was Fred who persuaded Ansel Adams to say this...

Probably right, Ralph, Fred uses the term "chalk" repeatedly in the newsletters.

There's a graph comparing specular and diffuse density in "Photographic Sensitometry" by Todd and Zakia. It clearly shows curve differences that support the argument that higher contrast is the only difference between diffusion vs. condenser. The graph shows greater impact on faster (grainier) film.

But a graph of spectral densities of a silver image is suprising. There's a sharp drop in density as you approach UV. 1.0 approaches 0.5 as you get closer to 300nm.

The text implies a neutral image (as opposed to stained). If this kind of curve is typical, it would be easy to see this working in favor of highlights - and I believe that UV in cold lights would have the advantage.

Now I will struggle with the difference to be expected from my densitometer with possibly less UV than my Omegalite cold light.

RalphLambrecht · Apr 29, 2010

Bill Burk said:
...But a graph of spectral densities of a silver image is suprising. There's a sharp drop in density as you approach UV. 1.0 approaches 0.5 as you get closer to 300nm.

The text implies a neutral image (as opposed to stained). If this kind of curve is typical, it would be easy to see this working in favor of highlights - and I believe that UV in cold lights would have the advantage...

What does this mean for VC papers and soft filtrations?

Advantages of cold light heads

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