I have the Picker book which shows the differences between cold light and condensor head prints. While I'd like to buy a cold light head for my Durst-Pro I've been reading that cold light heads are terrible for use w/ VC papers. Other say modern cold heads work better w/ VC. Anyone here have experience with this issue? Also, has anyone used the "Universal" 4x5 Cold Light adapter from Kienzle in Germany? Please advise.
There are some arguments about what he said literally and the whole context.
As you are doing, get the whole story (take the most complete answers you get!) from a number of people before discounting either method.
I think the problem with cold certain heads and VC paper is in the light spectrum of the specific lamp...whether it has compatible wavelengths for the blue & green that VC paper is sensitive to. Find out what type of lamp a given unit has before you bid/buy and research that lamp's spectrum.
A second complaint some people have with certain cold heads is variation of light output with temperature, especially from a cold power-up.
With a simple head that has no control system to regulate the light, some people leave them on at least 15 minutes and use a lens cap system to control the on/off of the exposure (momentary grammar lapse there).
Ole from APUG (I don't remember if he is here too or not) has a 27W CFL in his enlarger to replace a big incandescent lamp. He leaves it on & manually uncovers the lens and is very happy with the results. I know there are some variations in lap color temperature with CFL's, but you don't get to choose specific phosphors like you can with Aristo (Arista?) lamps.
I am short on names. links, etc. today, but the Scandinavian guy who handles the big enlarger refurbs & sales (Jensen?) has a lot of tech papers on his website on lighting technical issues.
Murray
Coldlights and VC paper work fine together. A lot of people use this system and I have for about 10 years now. I'm using a V54 tube from Aristo with filters under the lens. If I need more contrast than this, I add blue lighting gels above the neg to get a little extra boost.
Coldlights have inconsistent light output, mostly as a function of temperature. A closed loop timer/controller of some kind is best, but I have posted some data of coldlight output vs time and temperature here:
http://www.largeformatphotography.in...t=34298&page=2
It is down near the bottom of the page....
my picture blog
ejwoodbury.blogspot.com
The main issue with the older ones for VC paper was that they were too green, so people would add a yellow filter below the light source (I forget how much--on the order of 20-40Y) to start with normal contrast.
Newer heads with a V54 tube work fine with VC paper, and then there are dual tube heads dedicated for VC paper.
The ramp-time issue affects all papers equally. More modern heads have a heater circuit that improves the situation substantially by maintaining the temperature of the tube. The best option is a compensating timer with a sensor that measures the output of the tube and adjusts the exposure time accordingly.
I'm not sure it's just the newer heads that work well. I have an old Zone VI on my Beseler 4x5 and an even older Beseler cold light on my 5x7. The multigrade filters I have work well with both of them. Without a filter, with either head, I get about the same contrast (slightly more perhaps, but you'd really have to stare at the prints to see the difference) with Oriental variable contrast paper as I do with a box of Kentmere single grade fine art paper that they call equivalent to Grade 2.5. The Zone VI has more falloff at the corners than the Beseler. That's about the only difference. Another thing is that the Beseler head is quite and the Zone VI buzzes like a mother. There's probably something I should know about that.
I too have an acient Zone VI head on my Omega and find I get passable contrast control with Kodak below lens filters on a variety of VC papers. There is something a little amiss though as the difference between half grades above 2/12 is bigger than it should be.
I use an RH Designs Analyser Pro and find the metering functiuon very useful at testing the consistency of the output. This one has a heater but doen't return a consistent reading for about 10 minutes after it's first turned on. During the session it stays pretty stable without having to be left on all the time.
If you want to try for a cold light effect before buying just insert a diffusing disk in the light path as close as possible to the negative stage.
The big advantage of color heads or the expensive two lamp VC coldlights is you can adjust any contrast without having to do two separate exposures through two filters to get needed contrast. I'm always finding I need something inbetween the filters.
If you work in a set way, say exposing and processing the print then doing a second exposure, things will be pretty stable. But if you want to expose say 10 prints one right after the other you might see some differences between them. For that case you need a stabilizer or compensating timer.
Also many people say cold lights and condensor heads will produce comparable results if the negative contrast is adjusted properly. I'm not sure as I never really used a condensor head. But the articles I've seen were written by some very knowledgeable people so I assume they are correct.
Also if you try a cold light look for the newer V54 lamp from Aristo as it's made for VC. Might as well start out with one if you are buying.
It depends on the paper you plan to use. Download the specs on the paper of interest. Kentmere VC FB warns that you may not get good results at the extreme Ilford numbers 00 and 5. For a while I was happy with this printing mostly at between 2 and 3. Then I got interested in Les McLean’s version of split grade printing where you only use 00 and 5 filters. I use this rarely when the range of light in the original shot is more than about five stops. Ilford Multigrade claims there is no problem. I plan to try it next. I use an Aristo 12x12 head on a Durst 138S converted for 8x10 negatives.
John
Thanks guys. You gave me a lot to chew on. I will continue my reserach. By the Jens Jensen is producing a very interesting light source which is supposed mimic condsensor, diffused, cold and point light sources through the same head.
My personal experince was with a newer Zone VI head with the V54 lamp and a Metrolux timer. I could get consistent exposures after allowing for a little warm up time at the start of the session. After a lot of experimentation with various vc papers and both Kodak and Ilford filters, I found that there was unequal spacing in the grades - especially in the higher contrast end where there was not much difference between 3 1/2 and 5.
I always thought Fred Picker muddied the water in his discussions of cold lights as being the only solution. The solution to the problem that he was trying to address was a diffusion rather than a condeser light source. There are other diffusion sources than a cold light - color heads are one example.
In the end, I sold the Zone VI and bought a used Chromega D for $100 for my D2 and now dial in the filtration. The results have been consistent, fine-tunable,and I have had no heat (negative pop) issues since the head has a good blower incorporated. It has been a much better solution for me.
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