cold light and diffusion lightgreenspun.com : LUSENET : Large format photography : One Thread
I was wondering what the benefits are using a cold light source over diffusion. I use Kodak Polymax Fine Art multigrade paper and T-Max 400. It seems like a lot of you use cold light, and I'm wondering if I'm missing out on something. I'm actually going to be shifting from condenser to diffusion in the near future, and I was looking forward to not having blocked highlights due to the Callier effect. And I believe diffusion creates more tones. I never really seem to have a problem with dust. I'm curious what the "cold light" has to offer.
-- Raven (email@example.com), September 12, 2000
Absolutely no difference.
There's no magic to it, it's just another light source. The cold light tube has to pass through a diffuser, same as any other uncollimated source.
No light source can add tones.
Of course, I'm going to get an argument over this, but let me add that I've used cold-cathode, condenser, and halogen-diffuser enlargers, in most formats from 35mm to 10x8, and I can tell you that none of them are magic.
There is something a bit eerie about the light from cold-cathode; it disturbs the eyes, and I find it difficult to focus properly on the baseboard image. I think this is the root of the 'glowing' reports that cold-cathode fanatics give.
The photographic paper sees none of this. Cold cathode just gives the same bog-standard images as a diffuser source. In fact, you can probably get the same eerie effect on the eyes from a colour diffuser head, by simply dialling in a blue bias.
-- Pete Andrews (firstname.lastname@example.org), September 12, 2000.
Pete's comment about the "eerie" light from cold-cathod is interesting, for you get the same sort of glow from the blue/green focusing light on Ilford's Multigrade 500 head. And again this is difficult to focus with the unaided eye. Its not until you use a good quality grain focusing device that you realise how positive it becomes in focusing. The grain is either sharp or its not, there is no inbetween like you get with some light sources. Regards,
-- Trevor Crone (email@example.com), September 12, 2000.
Raven, As stated above, there is no difference whatsoever between diffusion light sources. These inlude color heads with mixing chambers, cold light heads and anything that doesn't pass through condensers. Collimated or point sources are different from diffusion sources in that, due to the Callier effect that you mentioned, increase contrast. This can be compensated for by adjusting the development time for the negative. Color work is usually done with a dichroic head, and is therefore diffusion printed, but one could use a standard condenser head and color filters to print color if one wanted the extra contrast. This is usually not the case.
Many also feel (myself included) that collimated and point sources accentuate the defects (scratches, dust, etc.) on the negative and that diffusion sources make for less spotting. Sometimes defects that print clearly with collimated sources just don't show up when using a diffusion source. This, in my estimation, is the real advantage to diffusion. The question of which diffusion source to choose depends on whether or not you plan on doing color work (in which case a dichroic head would allow you to do color as well as VC and graded B&W), variable contrast black and white (which might justify a VC cold light head) or graded paper black and white (which would only require the simplest and cheapest cold light head). Of course, if you are on a budget, you can print VC B&W with a regular cold light and filters. However, cold light heads are not suitable for color printing since they do not emit a continuous spectrum of light. The main advantages of cold light over dichro diffusion heads, in a nutshell, are: relatively fast printing times due to high light output and that they are considerably cheaper than a dichro head if you only plan to do B&W Hope this helps with your decision. ;^D)
-- Doremus Scudder (ScudderLandreth@compuserve.com), September 12, 2000.
There is not any difference that I can tell between a diffusion head and a cold light head. There may be a little difference in the evenness of the light in some of the older heads, but not much. The color heads with the diffusion chambers work great. There is a difference between the cold light or diffusion heads and condenser lighting. After I got a cold light head for my ol' D-2, I ran some tests between the heads. The difference is considerable in the highlight range. I have used the color heads for printing black and white at work, and they do a great job. The only downside is that if you intend to use only b&w, the cost of operation is much higher with the color head. The bulbs are expensive and don't last long. Stay away from the pulsed xenon type. They are a pain in the butt to use and the bulbs burn out easily on long exposures, and they ain't cheap.
-- Doug Paramore (firstname.lastname@example.org), September 12, 2000.
Pulsed Xenon. Now there's one that I haven't used. I thought that was only used in cine projectors, you live and learn! You'll be telling us that there's no magic in that light source either, I suppose, Doug? (Boo hoo. There must be some shortcut to stunning print quality) :-(
-- Pete Andrews (email@example.com), September 12, 2000.
If you develop and tailor your negatives to fit your light source, any one will work well. While a diffusion source may tend to suppress minor scratches & lint or whatever, it is no better or worse than a condenser or point light source. Fine tune your negatives to fit your enlarger light source and you will get good results. Some fine printers have used point light sources and others have used cold light heads.
-- Dan Smith (firstname.lastname@example.org), September 12, 2000.
You may also want to get your hands on a two-part series by Ctien that ran in Photo Techniques about a year ago comparing enlarger light sources. (It's possible the same information is in his book Post Exposure.) My (simplified) recollection of his conclusions is that there was no meaningful difference between cold light and mixing chamber diffusion and that the main difference between those two and condenser was that condenser had more contrast (pretty much confirming what everyone here has been saying).
-- Chris Patti (email@example.com), September 12, 2000.
All the respondants are correct. Other than dust and other detritus the light source should fit the neg contrast range and perfect prints will evolve (HO HO). The only thing you have to watch with cold light is that the filter # does not match the "graded" paper #. You must test the VC paper you are using as per Howard Bond's article in Photo Techniques. George Nedleman
-- George Nedleman (firstname.lastname@example.org), September 12, 2000.
The main difference between cold light sources and diffusion heads is the cost of maintenance. Through thousadns of prints I have never spent anything on cold lights (after the initial purchase). The halogen bulbs in diffusion heads can be expensive to replace. As noted many times above, there is no discernable difference in the prints. Make your choice and have fun.
-- Darron Spohn (email@example.com), September 13, 2000.
Isn't there some confusion in terminology going on in the question and some of the responses? What do you mean that you are wondering what the benefits are of using a cold light source over diffusion? Cold light sources are diffusion sources. At least I'm not aware of any cold light source that uses condensers. While there are diffusion sources other than cold lights (e.g. dichroic heads), AFIK all cold light sources are diffusion light sources. If you're asking about the benefits of cold light heads over condenser heads, that debate went on ad nauseum for years, largely because of Ansel Adams' claims carried on by Fred Picker and others, that cold light heads were inherently superior. I thought that recent tests and writings pretty well disproved that idea and that now it's accepted that as long as the negative is developed with the particular kind of light source in mind (less contrast for condenser heads), cold light heads aren't superior to condenser heads in terms of the quality of the print each is capable of producing.
-- Brian Ellis (firstname.lastname@example.org), September 13, 2000.
I think we've all said the same thing enough different ways, maybe we can put this one to rest. Regards, ;^D)
-- Doremus Scudder (ScudderLandreth@compuserve.com), September 15, 2000.
I knew nothing about the cold light head, so I thought this would be the perfect venue to learn. Thanks for the responses. Oh, and Mr. Scutter, if you can't contribute an educational response, then please, just don't!
-- Raven (email@example.com), September 17, 2000.