Aristo cold light without diffusion panel?

I searched for an answer to this question before posting.

 

I acquired an Aristo 1212 cold light with W45 tube several months back

and have not used it much because of a few problems. One was that I

filtered the light to "correct" to the right color light for using VC

papers, which made the exposures very long, with just a dim image on

the easel to work with. I just purchased and installed a new V54 tube

and it it only about 1/3 stop brighter than the old tube. I realize

that just by not having that extra filter to correct the color will

give me more light output, but I'm wondering if anyone has tried,

with success, removing the diffuser and using the bare bulb to get

more light output. Negative damage is not a concern with a shattering

tube because I am using a glass negative carrier.

 

I also had to remove the frame around the diffuser because I was not

getting full light coverage at the ends of the 8x10 negative. It

blocks about 1/2 inch all the way around the diffuser panel. This

particular problem may be caused because the diffuser is about 2-2

1/4 inches above the negative. To get it closer would require cutting

out the cast aluminum tabs on the Elwood that the cold light case

rests on.

 

If the diffuser panel were to be removed, the tube-to-negative

distance wuold be about 3 1/2 or so inches, probably far enough away

to give fairly even illumination.

 

I realize that someone will probably respond with "Why don't you try

it and see?" I have a limited amout of time and thought I'd solicit a

response or two from those who may have tried it.

 

Thanks in advance for any assistance.

 

DG

Without the diffuser, you run the risk of uneven illumination. Also, the further away the light source is (without the diffuser) the less diffusion there will be (in addition to less light output). Whether or not these issues turn out to be a problem for you, I can't really say.

Having looked inside my own coldlight, I'd guess that if you tried to use it without the diffuser, you'd get very noticeable bands of uneven density on the print, corresponding to the pattern of the tube. It may be true that the new lamp is closer matched spectrally to the sensitivity of the paper, which may increase your effective paper speed;and so decrease printing times.

Have you asked Aristo? I've called them several times with questions and they've always been very courteous and helpful.

David,

 

Cold light sources are generally intended to be as close as possible to the negative to improve uniformity. If your diffuser is that far from the negative, I think you will probably end up moving it closer eventually to get satisfactory performance.

 

Are you using a 240mm lens? You might also want to consider using a longer lens. The longer the lens, the more parallel the rays of light are that are being collected. This means that the light source can be smaller and still be acceptable, especially at the distance you have mentioned. I know that a longer lens is sometimes not an option.

 

I don't think that using no diffuser will work. Remember, the negative is not the light source (unless it is on a frosted backing). It is something that is held in front of the light source and holds back some of the light. So, you are essentially focusing on the negative, but the light source will be directly viewable through the negative. Granted, it will be out of focus, but by how much?

 

You may be able to get a translucent material with higher transmission properties than is supplied by the stock diffuser. There is a tradeoff, however. Higher transmission generally also results in less diffusion, which may mean that the lamps will start to become visible.

 

Most translucent materials are between 30% and 50% transmissive. If you went to a frosted glass, you might be able to get it up to 70% or so. Also, you may want to check on flashed opal glass, it may have a higher transmission rate.

 

Ground glass material, a piece of drafting mylar, or a piece of plexi that has been sanded might make a suitable diffuser, but you'll have to try them and see. With the plexi, lightly sand one side and try it. If it is not enough, you can lightly sand the other side. This will greatly improve the diffusion, due to the gap in the planes of the sanded surfaces. It will reduce the transmission, however, but I suspect it will still be higher than 50% by a good margin.

 

A call to Aristo would be my first task. They should be able to tell you what the performance specs are for their diffusion material. That will tell you if there is room for improvement. They may also be able to provide you with alternate material.

 

After that, I would go to a glass suppply shop and ask for some pointers. They should have various glass and plastic sources, and the performance specs for these should be available.

 

---Michael

I find your difficulty interesting, as if anything, I find my 1212 V54 head too bright - I requently have to stop down to f/32 to f/45 to get my exposures into the double digits. These are for 11x14 and 16x20 enlargements from 8x10 negs. All I can suggest would be to talk to Arista, as it sounds like your bulb might not be burning as brightly as it should.

Machine the tabs away on your Elwood, so the 1212 can go right on top of the Neg. holder. Then you will not have cut offs and the light source will behave as a true diffusion head (which is not the case if you move the light source away from the neg.) I use a 300mm El Nikkor with a 1212 head; tons of light...no cut offs...totally even lighting

David,

 

Your 3.5 inches distance between the tube and the negative is far too big. Your lamp must not be more than 1 ich away to provide full light density.

This is somewhat off-topic but I'm extremely curious why people buy cold lights? Cold lights are fussy and require feedback electronics to give consistent light intensity. A piece of Opal glass is a much cheaper way to get the advantages of a diffuse enlarger light source (the only advantage that a cold light has). Even better, if you have the money and someone makes one for one's enlarger is a VCCE head or color dichroic head. Fred Picker spread a lot of good technical photographic information but he also spread the now totally debunked idea that cold light is somehow superior to other diffusion mechanisms. I forgive him, but it does seem to take a long time for the cold light myth to be dispersed.

Cold light is one of the tools among various light sources available and should be treated as such. For one thing the uniform light spread may be easier to achieve than with condenser illumination, clearly an advantage for huge negative sizes. It is cold, therefore is better than your solution. It is also better than condenser light for printing very dense negatives, (inherent high power, opposite to what DG experiences are above) and sometimes it is simply fun to change one light source against the other.

Indeed, claims that CL offers better tonal range than condenser is a myth. My color dichroic head (Beseler) is too soft for my B&W negatives.

Britt, you answered your own question. Single tube cold light heads are cheaper than VCCE heads or color dichro heads, and work much better than a diffuser on a condenser head. When Fred Picker started his crusade to promote cold light heads, high quality variable contrast paper was not the norm. His main complaint was with condenser light sources, even if he thought that cold lights were slightly superior to other diffusion light sources.

Picker didn't just say that cold lights were slightly superior, he said they were so vastly superior that anyone using a condenser head was basically an idiot (take a look at the old Zone VI catalogs). Picker probably did a lot of good in promoting photography but he did a lot of harm too with his totally unsubstantiated personal opinions that were presented as absolute truths. More than one of Picker's "truths" was debunked by Richard Henry in his book "Controls in Black and White Photography." In fact if it hadn't been for Picker and David Vestal the book would have been a good bit shorter than it was.

FWIW, The Elwoods, at least the ones I've seen, are not condenser enlargers. With the oft missing/broken diffusion disk provides for a wonderfully even light. The next best thing I've found is a piece of ground glass as a substitute. If thats too fast, you can add another piece of gg on top of those 'tabs' and if thats still too fast, put an 8x10 gg on the top of your neg. 'sandwich.' A cold light would cut down on the heat---which is pretty intense---but I warm tortillas with my Elwood --- don't try this with pizza---the cheese makes a mess! If it gets too hot, an ice cold beer usually does the trick(ya drink it!)----------Cheers!

Brian, I don't think you read my post correctly. I said that Picker <i> �thought that cold lights were slightly superior to other <b>diffusion</b> light sources.�</i> Yes, Picker did say that diffusion light sources were vastly superior to <b>condenser</b> light sources. Personally, having used both condensers and cold lights for about 20 years each in succession, I agree with Picker.</P>

 

With regard to Richard Henry and his book <i>Controls in Black and White Photography,</i> rarely has there been such a �hack� job ever published. Henry admits that there is no difference is print resolution between a condenser and diffusion light source, that a diffusion light source shows far fewer negative defects (unless the defect is in the emulsion), and a diffusion light source shows virtually no dust. If the only other difference is print contrast, then one would have to wonder why people use condenser light sources, other than the obvious reason that they are cheaper.</p>

 

With regard to Henry's other findings, he used continuous agitation in his film development (to save time) and only tested two different films with only one or two developers. This completely distorted the contrast control and tonal gradation that most photographers strive for with intermittent agitation. Most of his conclusions are superficial and are based on small sample sizes and imprecise measurement methods.