a UV enlarger?

[Mainecoonmaniac]

I'm playing with the idea of converting my 45MX to a UV enlarger. There are new LEDs that emit UV light. I'm wondering if it would be practical to try to make a UV enlarger head for cyanotypes with LEDs? I've exposed cyanotypes outside doing contact prints and it can take up over 10 minutes in full sun. I can try to enlarge negs to do contact prints, but with a UV enlarger, I would just skip enlarging the neg.

[M Stat]

With a UV enlarger, focusing becomes problamatic. Considering the intensity required for UV enlargment, a standard grain focuser would burn out the retina in your eye, and a closed circuit video system must be employed to enable focusing. The beauty of negative enlargement is that you are able to adjust the contrast of the original negative to whatever level needed for various alternative printing methods.

[Hexavalent]

Optics with very good UV transmission would be required; such glass tends to be very $$

The Fresson lab employs enlargers for their process - exposures run in the hours.

[steven_e007]

I've thought about this, too, but never done anything about it. The usual reason for contact printing is that most lenses absorb UV, so the enlarging lens would normally pass such small amounts of UV as to make the developing out time far too long.

Lenses intended for UV are made of quartz or flourite, are very expensive and very rare.

With LEDs you can get quite a lot of UV, I suppose, without all the heat and high voltage of the old bulbs or the ungainliness of long UV fluorescents. As the other APUGer says, though, think about the safety of your eyes.

If you use a conventional lens, then the simpler the lens, the more UV it will pass. A very simple triplet may be a much better bet than a top quality 5 or 6 element job, but only expect to pass a few percent of the light from your LEDs.

So, would very bright LEDs + simple but very fast triplet = a working system?

I've no idea, but I'd be interested to know if you can make it work.

[anikin]

Hexavalent is right. Optics is the main problem. Regular glass blocks too much of UV, and you can jack up the power of light source only that much before melting your negative. You need to use a quartz lens for a reasonable exposure time. A lens that covers 35mm is very expensive. I did not find lenses that cover larger formats, but I did not look for too long. Anyway, it's not impossible, just very expensive to do. A very good idea though. I've been long contemplating making one myself.

Another possibility is to use a UV laser as exposure source. Do a raster scan through the negative. Doing that you may reduce need for expensive optics, but the cost of the light source goes up since you need a powerful UV laser (Blue-ray DVD burners, here we come!) and a high-precision raster mechanism. With that approach, an issue of vibration comes up as soon as you introduce moving parts.

I don't think focusing would be too much of a problem. I would coat a sheet of paper with fluorescent paint and use that for focusing.

[E76]

Durst Pro developed a UV lightsource for enlarging on Azo, so it's certainly possible. You are definitely going to need a extremely bright lightsource.

[JBrunner]

Could use mirrors instead of lenses.

[Mainecoonmaniac]

Wow. I'm learning a lot about UV light and glass. I guess most if not all enlarger lenses are made for the visible spectrum.

[Hexavalent]

Another thing to consider is the poor old negative - it's likely to get fried by intense UV; this does happen with Fresson enlargements.

[holmburgers]

Could use mirrors instead of lenses.

Hey, what about this though? JB might be on to something, there were old cameras that didn't use lenses at all. You could theoretically utilize 100% of the UV with a front surface mirror.