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

[John Layton]

Morning Musing...

It has been in the back of my mind forever it seems...that a barrier in using a conventional enlarger for alt process (PD/PT, Albumen, etc.) rests in the glass of a conventional enlarging lens, in that it blocks much of the UV light which is so necessary for anything approaching reasonable exposure times for alt process. In other words...even using a UV light source in a conventional enlarger for POP papers is very difficult...mostly due to the enlarging lens.

But how many folks remember that Hasselblad lens made of quartz...allowing it to pass UV light? Would such a lens, if used on an enlarger in combination with some highly tuned UV light source (LED?) make it a bit more convenient to print POP's by enlarger projection?

Wouldn't it be great if we could directly enlarge our wonderful negatives onto Alt-Process papers?

[Tin Can]

I made a 20X36" heavy glass on a bench, foam under contact printer

My 14X36" Camera is resting for a push

[Michael R]

Someone on APUG or here made a UV enlarger.

[Duolab123]

I think you would need carbon arc lights and then you would melt everything :cool: Duplicating the sun is the goal. Remembering the illustrations of ladies making POP contact prints, early Eastman Kodak, there was a arc source surrounded by contact frames facing inward like a Christmas tree.

Maybe Xray and magnetic lenses. :o

[Duolab123]

UV for slow chloride papers would be feasible.

[Mark Sampson]

Once, while at my former employer, I was asked to assist a different group who had an essentially similar problem. They had an Omega D-2 condenser enlarger; I found that a Dyna-Lite flash head was a close match to the Omega lamphouse. Not sure if the maintenance shop had to rig an adapter or not. So with that rigged, I attached a 2000 w/s powerpack and suggested that they have at it... set it t full power and just close your eyes when you press the button.
It *should* have worked... it was a secretive group, and I was very busy with my own work, so I never really found out. Except a couple of months later they gave back the Dyna-Lite gear, that research program having been cancelled (for reasons never mentioned).
I still think that approach would be a good one, though I doubt that I'll ever try it myself.

[Drew Wiley]

Most EL Nikkor enlarging lenses pass UV well. The problem with designing UV enlargers per se is the complication involving fire hazard, sufficient cooling, and risk to eyesight. You'd have to go to aerospace gasketing, sealants, and coatings. Not a simple undertaking. I've successfully enlarged onto slow contact printing papers like Azo using a conventional halogen colorhead; but alt UV processes are a different story.

[John Layton]

I should speak with my neighbor, Jon Cone (Cone Editions), who builds (under contract for various institutions) what are likely the most efficient LED UV light boxes on the planet. Efficient because he's using (lots and lots of) extremely narrow spectrum UV LED's, which I'm guessing could be utilized to create an enlarger light source. Lots of issues to be sure...but worth the conversations I think.

[domaz]

People have already used 100w COB LEDs to expose Carbon (https://www.youtube.com/watch?v=J7dYrWV_LKs&t=15s) in a improvised enlarger. I believe he has done Cyanotype as well.

Don't burn your house down or waste energy with Carbon Arcs....

[jnantz]

look into the lens the durst enlarger that Michael Smith used to enlarger his 35mm negatives onto AZO. I don't remember the details other than he was very excited, and it was brighter than the sun.

[Drew Wiley]

Durst L184 UV conversions were once offered by Jens at Durst Pro. I don't know how many he sold, but there were all kinds of heat issues. For that kind of thing you really need a stainless steel water jacket cooling system around the head. Huge pulsed xenon commercial units also existed for sake of the printing trade. Very expensive. Somewhere in my old literature heap I still have an ad for one. It would probably cost $150,000 to make today. An ancient carbon arc enlarger is still being used for the Fresson process in France.

[Jim Andrada]

IIRC movie theatre 35mm film projectors used to use carbon arc light sources.

[John Layton]

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?

[Tin Can]

I have many

UV 365 50 watt

My for my Alt

They now have powerful 365 flashlights'

https://www.amazon.com/Everbeam-Black-Light-Flood-365nm/dp/B0863HD955/ref=sr_1_18?crid=I8DHVWHKJ125&keywords=uv%2B365%2Blight%2Bspotlight&qid=1704547043&sprefix=uv%2B365%2Blight%2Bspotlight%2Caps%2C94&sr=8-18&ufe=app_do%3Aamzn1.fos.006c50ae-5d4c-4777-9bc0-4513d670b6bc&th=1

[John Layton]

Zeiss 105mm UV Sonnar:

https://www.zeiss.com/content/dam/consumer-products/downloads/historical-products/photography/hasselblad-cf/en/datasheet-zeiss-uv-sonnar-43105-en.pdf

[Drew Wiley]

A Sonnar is a taking lens that probably wouldn't be all that great in enlarger repro ranges. The question is just how much UV needs to get through and at what exact wavelength per specific processes. You can hook up with Sandy King on that question. He's tested the variables. The enlarger head diffusion system and carrier glass are going to factor, and not just the enlarging lens - and those other components certainly aren't going to be quartz! An EL Nikkor enlarger lens should be fine, given the fact that it passes more UV than most enlarging lenses, and that you'll need considerably more UV output anyway to overwhelm the various glasses above there anyway.

[Mark J]

Most enlarging lenses will pass UV down to 380nm and will be fairly well corrected at that point.
If you want more UV and power one logical step is mercury vapour which has a strong emission at 365nm. I would have to check where Xenon emits. However any of this will require a UV-specific lens.

[Drew Wiley]

There's a reason UV enlargers are rare, and also why UV contact printing from already enlarged second generation negatives is so common.

[MartinP]

A while ago we had a problem at work involving a mercury vapour light-source that was no longer supported. There is an optical-contractor who solves that sort of problem for us (one company service is metal-film lithography for special purposes). The result was a single UV led, a doublet quartz lens and an atmel chip to control exposure, coolling etc. I think the UV was a shorter wavelrngth than you would need (around 340nm for the photo-resist). The quartz lenses were from either Edmunds or ThorLabs as a stock item, so they weren't specially made, but there are some sorts of glass that have a reasonable UV-transmission for this wavelength and you might not really, really need to use quartz if you can use a longer exposure time. The parts assembly was only a couple of thousand in total, excluding machining a new housing.

Bear in mind that this was a 'simple', evenly-illuminated light-source, as we make our products by masking rather than projection. It is unlikely that you would be able to use this for projecting a negative with much resolution.

[Mal Paso]

My current enlarger has a 30 printing watts LED head and at low power it's almost too much. I think a UV LED head is possible given you devote most of the energy to UV and eliminate almost all the heat. On my enlarger even with the white LEDs on, green and blue at full power, 53 watts, the negative stage never gets warm. There's no IR. I've burned plates and negs with arc and it's mostly smoke and flame with a little UV mixed in. Like the tungsten bulb is 95% heat 5% light.

[Jason Greenberg Motamedi]

There is a lot about UV passing lenses on Klaus Schmitt's blog: https://photographyoftheinvisibleworld.blogspot.com/2011/01/uv-lenses-tested-good-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!:eek:).

[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!:eek:).

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".

[Maris Rusis]

UV enlarger? Is this relevant? An enlarger that can do cyanotypes might be able to do POP.
https://www.youtube.com/watch?v=zI1nWHuX3N0

[John Layton]

Interesting video...and scrolling down to the very last comment/question, regarding the possibility of using this enlarger for PT/PD - and that this goes unaddressed. Also...nothing mentioning actual glass (lens, condensers, etc.) types, relative to UV transmission, nor anything about other means aside from condensers of focussing/enhancing UV LED light paths - such as parabolic mirrors. My guess is that Mr. Krooshof has already vetted these possibilities...but maybe I'll try contacting him just the same.

At any rate...I just want to thank everyone here so much for not only the great information put forward, but also for being so patient as I've persisted in hammering away at this question.

[Drew Wiley]

Yeah, fun video, though I didn't watch all of it yet. And I have no interest in printing cyanotypes, though I do have some lovely antique ones in my collection.

[Alan Townsend]

Interesting video...and scrolling down to the very last comment/question, regarding the possibility of using this enlarger for PT/PD - and that this goes unaddressed. Also...nothing mentioning actual glass (lens, condensers, etc.) types, relative to UV transmission, nor anything about other means aside from condensers of focussing/enhancing UV LED light paths - such as parabolic mirrors. My guess is that Mr. Krooshof has already vetted these possibilities...but maybe I'll try contacting him just the same.

At any rate...I just want to thank everyone here so much for not only the great information put forward, but also for being so patient as I've persisted in hammering away at this question.

That video is one of the best out there but very lengthy. He doesn't mention the frequency or size of the custom made LEDs he ordered from china, but they must be near uv (395nm) and pretty small, although the quartz lens will make them optically larger. The plastic fresnel lenses would require near uv. He uses the classic cyanotype with a pre-flash exposure, which would require an extremely thin low density range negative with high transmission. Not exactly the type you want for platinum/palladium. Video is mostly about his journey in developing and building the equipment for projection printing cyanotypes without having a workshop. It was his learning process.

The majority of historical printing processes are quite sensitive to blue light as well as uv. If using pyro or other staining developers, this can affect the contrast. Sunlight has very little uv light getting to ground, much more blue is available. If you calibrate your process for a particular UV light, this can a problem when the frequency changes.

Parabolic reflectors would have to be off-axis segments to avoid a large hole in the center, so not very useful for condensers. Condensers don't need to be very sharp, either, so pyrex plano-convex pairs were used in enlargers like the Omega D2 with about F:2. Fresnels are much cheaper, and used in overhead projectors widely, some as fast as F:1. An Omega D2 can be converted easily using standard COB near uv LEDs for 4x5, but likely not practical for this use.

Personally, I enlarge my negatives using photographic means without resorting to digital negatives due to the challenge and the pleasure of working with photo chemestry. Anybody can click a mouse but that's not photography. I use mostly ortho-litho films for this and get good results. I will likely experiment with xray films this winter for this as well.

Alan Townsend

[Drew Wiley]

Fresnel lenses typically involve a kind of plastic which absorbs a fair amount of UV. So you need a surplus of it to begin with. With contone imagery, Ortho Litho film also tends to have a fair amount of resudual fbf and yellowness which blocks some of the UV; so again, sheer UV muscle is called for. Direct sunlight has lots of UV, and has worked since the inception of these processes; but it varies and takes longer. The first enlargers were based on capturing and directing window sunlight.

All this stuff is fun. I've made all kinds of specialized equipment myself. But if it were me, I go the enlarged duplicated negative route, and contact print it. I don't particularly like Ortho Litho for that application, but have certainly done it successfully.

[John Layton]

Kodak manufactured a really great emulsion for doing enlarged negatives back in the day...4125 I think? I understand that Bergger now makes something similar - has anyone here tried it?

To be totally honest...I've never really gotten deeply into PT/PD printing - but would like to try it again sometime. I do have fond memories of sitting out in the sunlight with a contact frame on my lap. A far cry from what I suggest here perhaps...but who knows, maybe I'll soon be out there again - letting nature work its magic!

[Eric James]

As a stepping stone, I wonder if it would be helpful to evaluate light sources by making contact prints through a polished quartz plate. They seem to be inexpensive.

[Michael R]

Kodak manufactured a really great emulsion for doing enlarged negatives back in the day...4125 I think? I understand that Bergger now makes something similar - has anyone here tried it?

To be totally honest...I've never really gotten deeply into PT/PD printing - but would like to try it again sometime. I do have fond memories of sitting out in the sunlight with a contact frame on my lap. A far cry from what I suggest here perhaps...but who knows, maybe I'll soon be out there again - letting nature work its magic!

I think Bergger Print Film is no more.

[Drew Wiley]

It's more likely to be synthetic quartz flats. Blemish-free natural quartz crystal of significant size is incredibly expensive. There was once a secret mine for that on a peak near where I lived,
which got in and out by mules. Even back in the 50's an optically clear crystal a foot long could fetch five thousand dollars or so. The exact location was a closely guarded secret and difficult to get to, and within a designated roadless zone (now an official Wilderness Area). When someone tried getting in there riding a Tote Goat, the Forest Service intercepted them 12 miles in, pulled the spark plug, and forced them to push the thing all the way back out.

[Alan Townsend]

Fresnel lenses typically involve a kind of plastic which absorbs a fair amount of UV. So you need a surplus of it to begin with. With contone imagery, Ortho Litho film also tends to have a fair amount of resudual fbf and yellowness which blocks some of the UV; so again, sheer UV muscle is called for. Direct sunlight has lots of UV, and has worked since the inception of these processes; but it varies and takes longer. The first enlargers were based on capturing and directing window sunlight.

All this stuff is fun. I've made all kinds of specialized equipment myself. But if it were me, I go the enlarged duplicated negative route, and contact print it. I don't particularly like Ortho Litho for that application, but have certainly done it successfully.

Drew,

Near UV behaves more like visual light with optics. Projector optics suppress near UV while enlarger optics have little effect. The 395nm uv leds have a fairly narrow band, but extend from violet through 360nm or so. Both cyanotypes and carbon print tissues respond about half as well to royal blue leds as to 395nm leds. I've measured this recently in testing I've done. I should have included this in my "internet photography lies"l thread. If I built one of these COB led enlargers, I would likely use a royal blue led array, since this is much easier to focus and almost as fast.

Ortho-litho film is quite flexible and about the right speed for darkroom work. For lowest contrast, I process using D23 at 1:7 dilution for 2 minutes with no water pre-wash. This gives a density range of about 1.4` outside on a sunny day. The film does have a nice curve to it, very similar to the curves for cyanotype/vandyke brown, so they can compliment each other. For the positive, I either enlarge 35mm to 4x5 or contact print 4x5 using the same enlarger, and post exposure flashing to fairly high densities to control the contrast. I also dodge and burn in at this step. The very curvey nature of ortho-litho makes it variable contrast via healthy flashing. This does increase the exposure time of enlarging the positives to the final negatives. By changing developing times to make the interpositives and negatives have identical curves with minimum flashing, a very linear curve results, allowing enlarging linear negatives to pretty darned linear negatives for carbon printing. Quite flexible when you figure it all out.

Alan Townsend

[Drew Wiley]

I would prefer to do that with FP4. But ULF sizes of that are way more expensive than Ortho Litho. And I prefer masking to flashing; but that means still more sheets of film. It would be getting prohibitively expensive at even 8x10 size if I didn't already have a stockpile of 8x10 film in the freezer. Last year I enlarged an 8X10 chrome original involving a total of 13 sheets of 8X10 film to achieve the master printing internegative. That's an exceptional quantity for me, but the end result was worth it. Dye transfer printers would routinely expend sixteen or more sheets of film per image.

Yes, carbon does need "thicker" negatives. But another application for the sheer brutality of ortho litho or Tech Pan would be making punchy internegatives for ordinary black and white silver printing from rather bland (low contrast) color negative films, via the double interpositive/internegative path. Yeah, I'd prefer to do that using TMax for both steps - but the remaining stash of Ortho Litho was getting lonely, and is a lot cheaper to replace. I souped it in HC-110. Great results, but way more fussy than TMax or FP4.