Quartz Lens/UV LED's for POP Projection Printing?

[Jason Greenberg Motamedi]

There is a lot about UV passing lenses on Klaus Schmitt's blog: https://photographyoftheinvisiblewor...od-for-uv.html
There is also a database of macro lenses he built which includes information on UV: http://www.macrolenses.de/objektive_sl.php?lang

[Alan Townsend]

Lots of heat keeps creeping into this discussion...so I must repeat myself: what I am proposing here is to utilize a quartz enlarging lens, which would maximize the passage of UV light, which could very well allow use of a much cooler UV light source (LED's), especially in light of advancements in UV LED technology - allowing the prospect of creating alt-process works such as PT, PD, Albumen, etc. by enlargement, logistically feasible.

...and while I don't know much about quartz optics except that Hasselblad created one awhile back, nor do I know about how this (quartz optic) technology could be utilized to create optics for projection enlarging, my guess is that a feasibility study could be done now with one of those Hasselblad UV lenses and an array of UV LED's. And even if that particular lens design may not lend itself to projection enlarging, it could still be utilized for such testing. Agreed?

Hi John.

I looked into this a couple of years ago but scrapped it after a few experiments. If your OK with expoosure times of a few hours or maybe even a day, then it can be made to work OK using regular enlargers and optics using COB near UV lamps with 395 nm radiation of 100 watts or so. These are arrays of LEDs about 20x20mm in size, with additional condensers avalable that increase their effective size about 1.5 X more. These require fast condensers to image those arrays on a lens of fairly large aperture that can be critically sharp at almost wide open aperture.

Problems are:

1. Holding a large format negative extremely flat for such long periods of times may require glass carrier, or other extraordinary means.

2. Maintaining focus for such long periods requires greater mechanical stability of enlarger system than normal.

3. Possible reciprocity effects with printing materials.

4. Stability of printing materials with respect to time after sensitizing and drying may be a problem.

There are many YouTube videos and web pages on this topic, as another mentioned. Heat or UV optical issues with these is not really a problem. Optical stability definitely is. My feeling is you can get pretty good results with such DIY units, but for practitioners with great quality requirements it will be difficult.

Have fun with it as always,

Alan Townsend

[John Layton]

Hmmm...would I still be sounding too optimistic to suggest that the issues I see as persisting relate to the presence/amount of UV absorbing glass (such as those "additional condensers") in the optical path?

What about getting rid of condensers entirely and instead utilize front-surfaced (UV reflecting?) parabolic mirrors to enhance the efficiency of the UV LED's? Might this, in combination with a quartz enlarging optic, enable exposures short enough to allow a negative to be secured in a glassless carrier (but perhaps under tension, at least for larger sizes)? Or...do there exist flat optical plates made of quartz - which could be used in place of a plain glass carrier? (but if so, I'm guessing that these must be very expensive?).

(Ha! I was just envisioning a parabolic, front surfaced mirror...redirecting the rays of the sun - through the negative, through the quartz enlarging lens to the paper below...and then - kaboom...instant firestorm!).

[Michael R]

Hmmm...would I still be sounding too optimistic to suggest that the issues I see as persisting relate to the presence/amount of UV absorbing glass (such as those "additional condensers") in the optical path?

What about getting rid of condensers entirely and instead utilize front-surfaced (UV reflecting?) parabolic mirrors to enhance the efficiency of the UV LED's? Might this, in combination with a quartz enlarging optic, enable exposures short enough to allow a negative to be secured in a glassless carrier (but perhaps under tension, at least for larger sizes)? Or...do there exist flat optical plates made of quartz - which could be used in place of a plain glass carrier? (but if so, I'm guessing that these must be very expensive?).

(Ha! I was just envisioning a parabolic, front surfaced mirror...redirecting the rays of the sun - through the negative, through the quartz enlarging lens to the paper below...and then - kaboom...instant firestorm!).

And how would you safely manipulate exposure (burn/dodge etc.)?

For alt printing, contact digital negatives are where it's at. Total control.

[Drew Wiley]

Dodge/burn etc would best be done automatically via supplementary registered masks. Otherwise, welding goggles and infinite patience; expect severe sunburn on exposed hands; not a good idea.

I wonder if I still have my old prototype sketches for an 8X10 UV enlarger I never built. I estimated the weight of the double-walled stainless steel water jacket and inner mirror box, when filled, plus all the other stuff up there, at around 200 lbs.

John - my old Durst color mural enlarger did employ a pair of actual quartz parabolic mirrors. But even with just high-wattage halogen light, the optical coatings would spall off prematurely;
and replacement cost or re-coating was very expensive. The Durst custom halogen colorheads made for the NSA had to have all their coated elements replaced every six month, with a lot of light gasket replacement issues too.

[Michael R]

Dodge/burn etc would best be done automatically via supplementary registered masks. Otherwise, welding goggles and infinite patience; expect severe sunburn on exposed hands; not a good idea.

Exactly. That's why you make an enlarged inkjet negative that already has the adjustments baked in. Customize it for whatever process you're using. Done and done.

[Drew Wiley]

Before scanning and inkjet output, they'd enlarge it all onto big graphics films suitable for big duplicate negs. In that case, the controls could be built in either through registered masks (ideally), or else actual hand dodging and burning. That is still hypothetically possible; but the availability of such films has drastically diminished, while the cost has drastically increased.

[Michael R]

Before scanning and inkjet output, they'd enlarge it all onto big graphics films suitable for big duplicate negs. In that case, the controls could be built in either through registered masks (ideally), or else actual hand dodging and burning. That is still hypothetically possible; but the availability of such films has drastically diminished, while the cost has drastically increased.

Yeah to me, at this point the prospect of multiple generations/layers of large silver masks is totally cost-prohibitive so if I were doing any alt processes I'd definitely be doing the inkjet negative thing. I've watched some of Bill Schwab's videos about it and it looks great.

Alternatively one could make non-silver selective masks a-la Alan Ross. Those should work.

[Drew Wiley]

Or there is the old time option of layering up dilute red creosin dye directly on the neg, or even smudge pencil directly on the neg. Only a few sheet films still carry a retouching surface, and it's better to do even that on a separate registered sheet of frosted mylar anyway. Alan's method is more equivalent to just general area dodging and burning, whereas true film unsharp masking can adjust even tiny details; but I sometimes do these things in combination - whatever works, and the more tools in the toolbox, the better.

Then there are a lot of contact printers who don't even bother. They expect the negative to be suitable in the first place. The great early platinum printer Emerson thought of dodging and burning as almost sinful or cheating; he called it, "sundowning".

[Tin Can]

Agree

Or there is the old time option of layering up dilute red creosin dye directly on the neg, or even smudge pencil directly on the neg. Only a few sheet films still carry a retouching surface, and it's better to do even that on a separate registered sheet of frosted mylar anyway. Alan's method is more equivalent to just general area dodging and burning, whereas true film unsharp masking can adjust even tiny details; but I sometimes do these things in combination - whatever works, and the more tools in the toolbox, the better.

Then there are a lot of contact printers who don't even bother. They expect the negative to be suitable in the first place. The great early platinum printer Emerson thought of dodging and burning as almost sinful or cheating; he called it, "sundowning".