Light source for Pt-pd and azo enlarging

I am contemplating building a light source for enlarging on pt-pd and

azo paper. My considerations at this point are two fold.

1. These emulsions are sensitive to UV light in the upper band of 350-

475 nm. Since this is largely invisible the problem of focusing on

the easel is apparent. I could incorporate a conventional light

source that would be switchable for focusing only. Would I experience

focus shift when switching to UV?

2.Additionally without getting into the matter of condensors the

source will be built as diffusion. Does UV reflect in the same manner

as visible light? Do conventional multicoated enlarging lenses

transmit UV light in the same manner as visible light? These

emulsions are obviously much slower then conventional enlarging paper

and will require a high wattage UV lamp source. I have located a

source for these lamps. In order to gain repeatability the lamps need

to come to an established burn status. Would a shutter be applicable

to an enlarger?

 

Any insight or information will be greatly appreciated.

Hi Donald

 

I like it the easy way for AZO 8x10 inch from my 4x5 inch negs I only use my Jobo LPL with a 200 watt bulb but I put the color head on it with 100 cyan because AZO loves the blue part more ( it is blue sensitive ) I get times for enlargments from 1-5 minutes with f 8!

Good luck!

Head for Ed Buffaloe's www.unblinkingeye.com. Lots of info on alt process and a big article on UV light for alt processes. Azo, being silver, will respond to an ordinary light bulb. Most everything else needs UV. Depending on how handy you are with tools, you can DIY or you can buy a UV light source.

I guess this might work but there must be some good reasons why for 100 years or so platimun and AZO have been limited to contact printing. Good luck though, if you can make it work it certainly would be nice to not have to worry about enlarging negatives or carrying around an 8x10 or larger camera. I do remember reading somewhere recently about someone who was using a 1000 watt light or something like that in his enlarger to enlarge onto AZO. I don't think he enlarged onto platinum paper though.

 

I've never used platinum but I do use AZO and I have done alt processes such as gum, van dyke brown, and cyanotype. FWIW, my exposure times with a 75 watt household light bulb for AZO run in the 30 - 45 second range with the bulb about two feet above the easel. My expousre times using the specialty UV lights required for these three processes in a light box I built myself, where the lights are about three inches above the easel, were in the five to ten minute range as I recall. My point here is that even if it's feasible to get a light source bright enough to enlarge onto AZO, it may not be anywhere near bright enough to enlarge onto platinum.

By way of additional information, I spoke with Durst Pro yesterday. They have developed a light source for their 8X10 enlarger that will enlarge onto Azo. The wattage is an incredible 5000 watts. The cost of the source itself is $5,500 and the complete enlarger with source is $12,000. This will allow usage on both conventional and Azo paper. They are also releasing a 5X7 enlarger in March that will be usable on only Azo and Platinum (no conventional paper) and the cost of that unit is slated for $5,500 at this time. So the technology exists, but my concern is that I would like to not have to replace my existing enlarging equipment if at all possible.

5000 watts? I sense a serious heat problem.

 

And $5500? You'd be better off buying a big camera and contact printing anyway.

Did you talk with Durst about using this equipment to enlarge with platinum paper as well as Azo?

Yes, they brought up the light source would be suitable for that purpose as well.

If it can expose both Azo and pt/pd I sense both a heat problem and a UV problem. If it puts out enough UV for platinum prints, there is a real safety problem here.

Donald,

 

$12,000 for a product that won't do as good of a job with platinum as a $100 home built fluorescent printer? That doesn't sound like a good idea to me. If you want to do platinum, make enlarged negtives, and print it in the traditional way. At worst, you could spend about $500 on a used Nuarc on E*ay that will perform very nicely. I managed to get one for $82 (OK, I was a bit lucky... they didn't really know what it was.).

 

Better yet, get a larger camera, and shoot for platinum on the right size in the first place. Part of the beauty of platinum is that it is a contact print. No grain, very high detail, and excellent tone. Start enlarging, and much of this will be lost. Certainly, some enlargement can be done without completely losing the qualities of platinum, but the second grain is perceptable, you've defeated the reason to use platinum, IMO.

 

I'm working on an 8x10 enlarger to enlarge my 8x10 negatives to 16x20 internegatives for this very reason (Sometimes it just isn't practical to take the 12x20 where I go...). That's only a 2x enlargement, and I think that may be close to the limit that I will want to do. Any larger, and I think things will start to fall apart. I'll never understand why people take 35mm negatives, enlarge them and print them on platinum. I guess it is the 'mistique' associated with platinum.

 

Since platinum has such a long scale, (approaching 2.0 of you wish to avoid restrainer) how are you going to handle the loss of contrast associated with enlarging? Your negatives will have to be even more contrasty than for a contact print to overcome the inherent fog that will be built up by the enlargement process (Remember, the long scale means that even a little fog will go a long way...). This is why an enlarged negative is a better solution. The contrast of the enlarged negative can be 'souped' to set it properly for a platinum print. This cannot be done straight to the print.

 

Before you try this, you may want to see what their enlarger can actually do. Compare it to the best traditional platinum prints out there. If you can tell no difference, then maybe it is a viable method to attempt. I doubt it will match up to what is possible with traditional methods.

 

---Michael

Michael is absolutely right. The best solution for Azo printing is also the cheapest. A light bulb. You can use the sun for free to expose pt/pd.

Dan,

 

Darn, I forgot about the Sun! So, it can be done for free with a split back frame. But only using a printing out method, like the Ware Method, or the Ziatype. Regular develop out methods are a problem, unless you have extremely consistant daylight availability (which is not too common in the US, I'm not sure about other places).

 

I have heard that some people use a Metrolux timer with the sun to good effect for develop pout printing. I have not tried it, but it could work, as long as the Metrolux timer has sensitivity in the right range.

 

---Michael

If you really want to enlarge onto contact-speed material, use a studio strobe head as the light source. Of course connect it to a big pwer pack. pop-pop-pop- there's your exposure, and 5000K as well. The modelling lamp will help you focus. When I did something similar, I used a 4x5 condenser Omega and a Dyna-Lite 2000 w/s pack, and a standard head instead of the Omega lamphead. That was what was to hand- you could do anything similar.

In Sullivan & Weese's <i>The New Platinum Print</i> the authors refer to Thomas Eakins using a heliostat to enlarge onto Pt/Pd paper. Apparently a heliostat was a sun-powered enlarger using mirrors to pipe down the light and track the sun. Not a solution that appeals to me, but it might provide a line of inquiry for research.

<P>

I'd adapt a Speed Graphic focal-plane shutter to the enlarger to control exposure. High intensity UV lamps need to be left on, not cycled.

<P>

Finding a lens might be a bigger problem. You'd need to find a lens that not only transmits enough UV to be useful for Pt but focuses it along with visible light at the easel. Regular enlarging lenses do not do this. Good thing those UV-Nikkors are so cheap!

<P>

You can buy frosted quartz glass for diffusion, but I couldn't tell you if it transmits enough light to be useful.

Building an ultra bright enlarger should only be attempted by someone with technical knowledge and mechanical and electrical aptitude and experience. If you make a mistake, you could start a fire, electrocute yourself, or become blind from UV light (depending on the light source).

 

There is published information that serves as useful input to a design for an enlarger for Azo.

 

Kodak publication G-10 for Azo Paper (available from Kodak's website) has a Spectral Sensitivity Curve for Azo. The graph covers the range from 250 to 750 nm, but the data is only plotted above 350 nm. The paper has NO response to light of wavelengths longer than about 460 nm. The response rapidly increases with shorter wavelength -- note that the vertical axis is a log scale.

 

For enlarging lenses, Nikon advertises that their lenses are corrected over the range 380 to 700 nm. Rodenstock's brochure for the 150 mm Apo-Rodagon-N shows the Longitudinal Color Aberration from 438 to 678 nm. Schneider's brochure for the 150 mm Apo-Componon (available at Schneider's website) shows the Transmittance from 380 nm to 700 nm. The transmittance is decreasing shortward of 500 nm and steeply falls shortward of 400 nm. The transmittance at 400 nm is 80%.

 

I think that all commercial enlarging lenses probably have fairly similar behavior. It is an intrinsic property of optical glass that the variation of index of refraction becomes progressively worse for wavelengths shorter than blue, and also that the glass starts to become opaque for shorter wavelengths. (These two properties are in fact related.) The stronger variation of refractive index in the UV makes it harder to design an achromatic lens. Manufacturers intentionally select glasses and coatings so that the light transmission is blocked shortward of the wavelength for which they are able to achieve good achromaticity (see the book Applied Photographic Optics by S. Ray). You shouldn't have a problem with color-dependent focus shift with modern quality enlarging lenses -- they are designed to be achromatic over the wavelength range that they transmit.

 

Putting the two pieces of data together, an enlarger light source for enlarging to Azo using a COTS (commercial off-the-shelf) enlarging lens should produce a lot of light at 400 nm. Shortward of 400 nm, the transmission of the enlarging lens will rapidly fall. Longward of 400 nm, the response of the Azo paper is rapidly falling. The useful range is approximately 360 nm to 450 nm. Shortward of approximately 360 nm, depending on the specific lens model, the lens will have no transmission. Azo paper has very little response to

wavelengths longer than 450 nm and no response above 460 nm.

 

The goal for the light source is quite specific: light at 400 nm is best, with 360 to 450 nm being useful. The OLEC L1250 described by Sandy King (http://unblinkingeye.com/Articles/Light/light.html) might be the best light source. (The thumbnail spectrum for the L1250 is actually the L1252, but the full size spectra are correct.) (Also see

http://www.olec.com/graphicarts/OLEC_SpectramatchTM_Lamps/olec_spectramatchtm_lamps.html) (The L1252 might be better for contact printing of some alternative processes because it has more UV, but that UV would be blocked by the lens.)

 

With this light you would have to design a shutter for the enlarger because it can't be turned on and off quickly.

 

Apparently the OLEC L1250 is available from 1 kW to 5 kW. Perhaps it is obvious, but 5000 W is a lot of electricity. In the US, a typical household circuit can supply 1,800 or so Watts and the typical portable electric heater is 1,500 Watts. One will need a dedicated circuit and perhaps extra air conditioning capacity in the summer.

 

Generally condenser systems use the greatest fraction of the light. A quality condenser system (e.g., Durst) is an optical system designed to image the light source onto the entrance pupil of the enlarging lens. That means that if you add your light source to an COTS condenser system, to get even illumination that light source should be about the same size as the original light and it must be in exactly the same location. Another advantage of condensers is that you can switch condensers to efficiently use the light with a small negative.

A possible disadvantage of condensers is that their thick glass might absorb a substantial fraction of the near-UV light, so perhaps a diffusion system might be better. A diffusion system might be easier to tinker with until you get even illumination.

 

Obviously you want the enlarging lens with the fastest working aperture. For 4x5 negatives, this would likely be the Apo-Componon 150 mm f4 or the Apo-Rodagon-N 150 mm f4. These lenses would need to be stopped down something like 1.5 to 2 stops to obtain good sharpness in the corners and even illumination. They will work well at about one stop wider than the f5.6 models. While these lenses are expensive, using one is probably the easiest and cheapest factor of two reduction in exposure time.

 

Also obviously, there will be a lot of waste heat. To avoid scattered light fogging the image, the lamp will have to be in a sealed enlarging head, thereby trapping the heat. This is placing an electric heater into a sealed box! A forced cooling system (a fan) will be required, along with careful material selection (probably metal) to avoid the enlarger from self-destructing or starting a fire. The OLEC lamp works best with a the gas inside at a certain

temperature -- perhaps you should put a thermocouple on the exterior of the lamp and see whether the temperature is correct, either a value that OLEC tells you or the value the lamp reaches when running non-enclosed.

 

From the Kodak publication, the ISO paper speed of Azo is 4. Typical speeds of Kodak and Ilford enlarging papers are a few hundred, so Azo will require exposure times more than 100 times longer than most enlarging papers (depending on the spectrum of the light) for the same light source. These speed ratings suggest that a light source 20 or more times brighter will be needed to keep exposure times reasonable.

 

I rate making a enlarger light source for Azo as VERY difficult. Don't expect that your first effort will work correctly -- you will probably have to modify the design based upon experience. This might drive up the cost above your initial estimate.

 

Making an enlarger light source for platinum/palladium printing is yet MUCH MORE difficult. The process is significantly slower than Azo, and it apparently needs shorter wavelength UV light. If shorter wavelength UV is required, the enlarger lens will be a very large problem. It will be very difficult to find a suitable COTS lens.

someone in West Berkeley is giving away some wonderful stuff that may help you:

Hello all:

 

Inkworks Press is going direct to plate (it is the 21st century, after

all) and we're scrapping our trusty platemaker and screen camera. They

are yours for the taking... you just have to show up and pick them up.

 

The specs:

 

20" x 24" Auto Companica 6700 screen camera

 

Millington contact frame platemaker with an L-1250 olec lamp (works

for diazo and photopolymer).

 

Everything is in good shape and is working.

 

These items will go to the scrapyard if not removed by Saturday, March

22, so contact me ASAP or just stop by. We're in West Berkeley.

 

Grendl Löfkvist

 

Inkworks Press

2827 Seventh Street at Heinz

Berkeley CA

open 8-5 M-F

 

510.845.7111

 

(Apologies for cross-posting)

 

 

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