Making a UV projector for alt-process prints

AndrewBurns said:

Wow, I removed the LCD screen today so I could start working on a negative carrier and it is STUFFED. It's uhh... not supposed to be clear in the middle like that...

I couldn't see how bad it had gotten while it was installed in the projector, I did see some light leakage through the middle when projecting a black screen but looking at it on a light table I'm surprised it has been printing anything recognisable recently.

So that's another nail in the coffin of the digital UV projector idea I think, I might not even have run this screen with the UV light on for 100 hours and it's completely bleached. I don't think I could have given it any more cooling than I already am, and at the current UV power exposure times are still relatively long and inadequate for DAS carbon. I think the concept would still work for PVA-SbQ and silver gelatin due to their extreme sensitivity, but not for more traditional processes.

Of course the same thing could still happen to film negatives, but I guess the advantage there is A) exposure times will be much shorter and B) I can always produce another copy of the negative if the first one bleaches out/gets damaged.

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Wow! Thanks for posting that. That's a serious no go unless having a free stock of LCDs

Could we see some of the prints you're going to exhibit?

DjulLau said:

Wow! Thanks for posting that. That's a serious no go unless having a free stock of LCDs

Could we see some of the prints you're going to exhibit?

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Yeah I think that the LCD projector approach would still work for very fast processes like PVA-SbQ but the same bleaching effect would likely still happen only much slower. So you might get tens of thousands of prints out of an LCD rather than hundreds or less.

I don't have photos of all of the prints that I'll be exhibiting (about 12 or 14 all up) as they're currently off being framed however here are some that I do have photos of. They're all coffee toned cyanotypes made using this projector (all contributing to the cooked LCD!). The funny thing is that now the LCD is cooked and I'm going to look at taking a different approach to exposure they're all de-facto edition 1 of 1!

Very nice results and photos! Thanks for sharing. Editions 1 of 1 are good for selling I hope I will be able to achieve that someday.

I don't know PVA-SbQ. I've had a look at your thread about it but it seems very complicated to me.

They look great! Did you try cooling the lcd, perhaps with a fan? I think that matters a lot for longevity of the lcd.

Beautiful work!

DjulLau said:

I don't know PVA-SbQ. I've had a look at your thread about it but it seems very complicated to me.

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A brief introduction: PVA-SbQ is actually an important non-silver halide imaging process in the printing industry, used to create screen-printing masks for printing patterns on fabrics or cartons. Its advantages include the absence of hexavalent chromium or diazonium salts, making it quite friendly, and it's also cheaper than photoinitiator polymerization systems.

DjulLau said:

Very nice results and photos! Thanks for sharing. Editions 1 of 1 are good for selling I hope I will be able to achieve that someday.

I don't know PVA-SbQ. I've had a look at your thread about it but it seems very complicated to me.

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Cheers. PVA-SbQ won't be that hard once I figure out a workflow, including dilutions and additives. It definitely seems way trickier than gum or any of the metal-based processes but people do manage good results with it and it's so insanely fast it's worth the effort to figure out. One big attraction is that you can buy the raw emulsion in kg+ quantities for a reasonable price which makes all the experimentation I've done less painful compared to something like Pt/Pd.

avandesande said:

They look great! Did you try cooling the lcd, perhaps with a fan? I think that matters a lot for longevity of the lcd.

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Thanks! Yeah I've had a very powerful air blower on the LCD the whole time, on the order of 120 watts and loud enough you don't really want to be around the thing without hearing protection for a significant length of time. With the blower I measured temperatures of around 60 degrees Celsius on the surface of the LCD, without and I think the LCD would have failed in seconds. I'm not sure how much of the bleaching was from heat and how much was just from direct UV damage, but I don't think I could have done more to prevent it. Having separate polarisers from the liquid crystal would help with cooling and allow more robust polarisers to be used (and replaced as needed) but nobody makes a display like this in the resolution I'd want off the shelf.

Where does a normal person purchase SbQ? Because I sure can't find it easily on the web.

imgprojts said:

Where does a normal person purchase SbQ? Because I sure can't find it easily on the web.

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I got 1kg direct from this Chinese supplier, you dilute it at least 1:1 with water when using it, so it goes a long way.

Oh! So the SbQ is a pre made emulsion. Okay. That's actually pretty good. There's no messing around with mixtures. Okay Im going to try this.

imgprojts said:

Oh! So the SbQ is a pre made emulsion. Okay. That's actually pretty good. There's no messing around with mixtures. Okay Im going to try this.

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Yeah it's really good, if I had to mess around with making it myself I probably wouldn't bother. Just remember that the stuff is very sensitive, and probably sensitive to blue light as well (although I haven't tested that) so you actually need to work in a dark room with yellow or red light, unlike some other processes like cyanotype where you can get away with dim white light.

I had seen this video series previously:


It seemed a little much. But if you can literally buy it pre-made, that's a good deal.

Yezishu said:

my next step might be to further reduce the projection area (which would correspondingly increase the UV intensity, the current value is still not enough) to make it easier for some photochemical induced material deposition (in a sense, an kind of alternative process?). Finding a macro lens with a smaller magnification is easy (the difficulty in macro photography usually in larger magnification), the main problem is that they may not be suitable for those UV wavelengths.

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A small update. I recently managed to reduce the projected image to approximately 2.1 × 4.2 mm, achieving a 385 nm UV intensity of around 13,000 W/m² at 5A, which is approximately 250 times that of noon sunlight UV radiation. While the resolution is excellent (surpassing 10,000 PPI), the image is hard to see with nake eye.

The loss of light intensity is quite significant. It is known that unavoidable losses account for approximately 20%, with an additional 30% attributed to surface reflections from the extra lens and optical path design issues when try to guild light into Olympus UV Objective Lens.

Yezishu said:

A small update. I recently managed to reduce the projected image to approximately 2.1 × 4.2 mm, achieving a 385 nm UV intensity of around 13,000 W/m² at 5A, which is approximately 250 times that of noon sunlight UV radiation. While the resolution is excellent (surpassing 10,000 PPI), the image is hard to see with nake eye.

The loss of light intensity is quite significant. It is known that unavoidable losses account for approximately 20%, with an additional 30% attributed to surface reflections from the extra lens and optical path design issues when try to guild light into Olympus UV Objective Lens.

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Are you familiar with diffraction limits in optics / the rayleigh criterion? I don't know what lens you're using, but to achieve a actual resolution of 10,000 PPI you'll need your working aperture to be f/2.8 or greater, and as I know of no visible macro lenses which can achieve that I'm guessing a UV one would be very rare (though a lens from a photolithography press could probably manage it, if you can get your hands on one.)

All this to say, you can probably print a larger area of image and achieve the same actual resolution you're getting now.

Ethan Brossard said:

as I know of no visible macro lenses which can achieve that I'm guessing a UV one would be very rare

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No, those lens are quite common in the visible range. An f/2.8 aperture is trivial for small-format imaging, as long as large-area imaging is not required. Nearly all small-sized CMOS sensors feature pixel sizes below 2 um (~12,700 PPI). Any macro lens paired with such a sensor can hit that resolution—that's what they are designed for, there is a vast range of industrial lenses available. A budgett 10x/0.25 objective lens provides a 1.3 um theoretical resolution(if you talk about effective f-number, ~f 2.0), and Thorlabs or Olympus or Nikon carries 10x/0.4~0.5 NA options with even better performance, ·0.5 um. Similar to these is the Olympus Zuiko MC MACRO 20mm f/2.0 or Mitakon Creator 20mm f/2, as well as Moritex / Myutron industrial macro lenses, they are essentially microscope objectives. Usually, such lenses are not categorized as conventional photographic lenses because they lack infinity focus. However, they are highly acclaimed in photomicrography.

While UV loss and optical adaptation for limsited Lens selection are the main bottlenecks for UV application, they aren't really concern for visible light (e.g., 405nm), you have many lens. And it is not state-of-the-art photolithography tech here; Intel already hit the 2 um mark in the late 1970s, nearly half a century ago.

Quick update, I managed to make a test print using the UV enlarger and a 4x5 negative with classic cyanotype last night and the results are promising. My measured UV energy reaching the paper is nearly 10X what it was with the LCD screen and subsequently my exposure times are a little over 1/10 what they used to be. An exposure that would have been nearly 45 minutes is now about 6 minutes, which is a huge improvement and should massively help my carbon printing dmax.

I need to work on my negative holder though as it currently warps/buckles the negative resulting in some areas of the print being slightly out of focus wile others aren't. The negative seemed completely happy with the UV energy going through it, didn't heat up appreciably with a big fan blowing on it during exposure.