UV light and PD/PT

[Wayne Crider]

OK, I'm a novice here, but have been recently intrigued by the PD/PT process, an d as usual my mind, or what's left of it after the 70's, started wondering why a n enlarger couldn't be used to produce larger prints off a 4x5 neg. That's when I came across the quote below in a previous thread.

"the optics in an enlarger lens are not designed for UV light, which is the rang e of wavelengths that these mixtures are sensitive to. So, you would need to sea rch out some highly specialized enlarging lenses that will focus UV wavelengths (and not absorb or reflect them, as most optical glass tends to do.)"

OK, I didn't know enlarger lenses or heat absorbing glass absorbed UV light, and if it's true then I'm at the preverbial end of the line, but if it's possibly n ot totally correct, might it be possible? I'm using an old Bessler 4x5 with a co oling fan. Thoughts.

[Wayne_6692]

Check Ctein's site - I believe that I read in his book that the El Nikkors transmit (focused) light deeper into the U.V. frequencies that the other lenses. Other than that you may look on the Glenview site for a quartz lens. The older the lens the better I would suspect the U.V. transmission would be (as a very general rule), since they wouldn't have the exotic glasses and coatings to filter it out - doesn't mean there wouldn't be a focus shift however.

[Michael Mutmansky]

Wayne,

There's a reason that there is nobody out there doing enlargements onto pt/pd. I would be surprised if you were able figure out anything to make it plausable.

Here's why:

1. UV light is a problem for optics, unless they are specifically designed for it. There is a lens out there (called a "Gotar" if I remember correctly) that is spefically made for UV light, so that might solve the UV optics problem.

2. You need lots of UV light. You would need to change your light source in the enlarger to make much more UV light than it does right now. How much? I don't really know, but when my negatives take 5- 10 minutes under a full bank of fluorescent lights, you know it has to be a lot. Since the sensitivity of the pt/pd paper is somewhat set (+ or -, with restrainer added), if you want to do an 8x10 enlargement, you need to produce the same amount of UV light in an enlarger head as the bank of FL lamps produces incident to a contact print.

This will lead to a serious heat build-up problem, so much so that you would probably end up melting your negatives down. (Similar to what happens in a slide projector, or a movie projector. If slide projectors didn't have those massive pieces of heat resistant glass between the lamp and the slide...)

3. You need LOTS of UV light. I can't say that enough. The pt/pd process is not very sensitive, and there is another aspect to this that I haven't seen in the literature, but I am sure would factor in somewhere here. Even if you could keep the heat off the negative, you are still passing an extreme amount of high energy light through it. I would expect that the heat, combined with the light would result in a significant 'ageing' of the negative, which would result in some kind of negative failure. This may result in brittle negatives, or something else.

Picture this: to make a print, you need a constant amount of UV light, as I said above. Now, through optics, you are forcing all that light through a much smaller negative. What happens to the flux of light per unit area of the negative? It goes up as a square of the magnification you are using for the enlargement. Somewhere along the line, that's got to be bad for the negative.

There was some discussion about using fiber optic cables to make a UV enlarger that might solve the problems listed above, but at what expense? The FO light source would have to be able to handle at least 500 watts of power, and preferrably more like 1000 or more watts to have reasonable enlarging times (in the sub- 30 minute range).

Ultimately, I don't think there is much reason to try this, because I think the real beauty of pt/pd is the combination of the long tonal scale, and the high level of detail that a contact printed negative can offer. I have seen pt/pd prints made from enlarged 35mm negatives that I thought looked horrid, because there was no detail in the print. At that point, all you have is a somewhat flat, low dmax print.

---Michael

[David Willis]

Suppose you were able to get lenses to focus UV light accurately and precisely.

Suppose you were able to get a powerful enough UV source without melting everything.

My concern is, how would you focus the thing? UV by definition isn't visible, and I wouldn't want to peer through a grain magnifier under that much UV light.

DW

[Michael Kelleghan]

Enlarge the original _negative_ to the size you want using whatever duping film/inter-negative, etc. that you like. Then contact print the enlarged negative. The quality of the duping film and enlargement process will, naturally, reduce the quality of the final print. But if you want _big_, you get _big_

Mike :-)

[RICHRRD ILOMAKI]

Wayne:

I too spent much time and energy trying to prove generations of Pt/Pd printers wrong by trying enlarging: no go! The closest I could come was strobe lights in the enlarger head and that failed because I could never achieve constant output over the hundreds of flashes necesary. Don't wast your time!

Make digital negs as outline by Dan Burkholder (www.bladedeiris.com, I think)or shoot in-camera negs. The money I spent trying could have paid for an 8x10 camera.

Enlarging smaller format negs to full size positives, then contact printing to a negative works but it is time consuming- an entire 6 hr evening for 1 good one. What I found that DID work was to get an old 6x9 folding camera- an old Zeiss Ikonta or Balda, expose TMax 400 at 200, process in Split D- 23- 3 min in Soln A and 10 Min. in Soln B, then make a 6 x 9 contact print on 4x5 Pt/Pd paper of a suitable subject that filled the frame.

Miniature Pt/Pd prints are very valuable. Elton John loves 'em, and he can afford anything, and has just about as good a collection of photos as anyone, even Madonna.

Also, making a film negative of an enlarged colour slide works great on 4x5 or 8x10 Ilford HP5 developed to a Contrast Index of about .8. I have a beautiful, IIDSSM, 4x5 Pt/Pd print of a rose made from an Ektachrome slide enlarged onto 4x5 film.( All the enlrging must be done in total darkness of course, and one must cloak most enlargers as they throw off a lot of stray light which will fog the film)

Palladio( sura.steinberg@napc.com)has instructions for making a light source for less than 100 bucks and sells chemical kits, as do Bostick & Sullivan.

Stick to it-its worth it.

Good luck

[Wayne Crider]

Well it appears that to do so would present many many problems that would have to be overcome, and it's starting to look like a 8x10 camera might be in my future. I can't help wondering tho about those tanning beds and the UV light that they emit, as well as the heat factor. In fact I would like to know, and I'll probably have to do some interent researching here, as to just what amount of UV light is present from a sun on a clear day. I know here in Florida that we get a daily UV index, which is usually quite high, and having done some reading on the PD/PT process, I know that the process of print exposure is way less than what we would ordinairly get laying on the beach.

Being in the air conditioning trade, and having done quite a bit of previous research on UV from a anti-bacterial point of view, and having installed UV light sources for the purpose of keeping clean, air conditioning systems, I know that UV has a wide range of frequencies, which is measured in nanometers. Not all can be used in a anti-bacterial way. Maybe there is a certain freq that may be more useful than others? I also know that the sources with which I work are very determental to plastic. In fact, it will eat it right up. So, the primary considerations are; quanity, or maybe more specfically frequency of UV light, dealing with the heat issue, and focusing the rays thru glass so as not to block it. One point, the UV lamps that I use emit a real light that is kind of blue colored. Exposure to eyes is not recommended.

[Michael Mutmansky]

Wayne,

The germicidal lamps work in the UV-C range, with the peak emission at 254 nm. My understanding is that the pt/pd sensitivity peaks in the UV-A range, so these lamps are not recommended for pt/pd printing, even if there weren't serious health issues involved with using them.

Tanning lamps operate in the UV-B range, but again, there are health hazzards with theire use. Ultimately, the lamps that peak in the UV- A range are the best, and safest to use.

There was a recent article on www.unblinkingeye.com written by Sandy King regarding the selection of UV light sources for alternative printing. You should look at it; there's a great deal of good infomation in the article.

---Michael

[Pete Andrews]

There was a UV transmitting Medical-Nikkor made about 20 or so years ago. I think it was a 200mm focal length, so that would be suitable. It may still be available to special order, but be prepared to take out a second mortgage to buy one!

All normal glass absorbs UV quite strongly, and any enlarging system will have to be designed as glassless as possible; so a condenser system is out of the question for the light source. This basically leaves you with the option of an array of UV tubes or bulbs, and a diffuser. The diffuser material is going to be a problem too. Most types of plastic absorb even more UV than glass does. Maybe you could get away with a thin sheet of matte polyester film, if it doesn't melt.Only Quartz glass is heat resistant while allowing UV to pass reasonably freely, but again, you're looking at a big outlay for a small sheet of glass.If you think it's worth the time and cost, then it can be done, but personally, I think that enlarged internegs are a much cheaper option.

[Michael S. Briggs]

An excellent article on UV-light for contact printing alternative processes is at http://unblinkingeye.com/Articles/Light/light.html. The author, Sandy King, experimented with various light sources.

Information given: both UVA and UVB work, but the longer wavelength UVA should be used because it is safer. Probably the easiest approach is a bank of UV emitting fluorescent tubes. For Pt/Pd, Super Actinic bulbs work well. BL and BLB will work too. The article gives much more information on the bulb types.

Another approach involving less do-it-yourself work is an HID lamp.