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Cyanotype's are developed with exposure to UV. I'm thinking of playing around with very large cyanotype, starting with a digital image. At first thought I wanted to use a LCD projector to fix the image. Then I read up on Cyanotypes and realized I needed UV, not visible light.

Is there a way to convert a projector to emit UV? Or... is there a way to make large cyanotypes from a digital image.

(By large I mean feet, think 2 foot by 4 foot...)

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    Some 3d printers use modified DLP projectors to cure resin that is UV reactive. It doesn't take much imagination to visualise a device that either moves the projector or the surface being exposed, to increase the total area that can be exposed. You may find that 3d printers of the future can be refactored to make large, high resolution cyanotypes. – dav1dsm1th Dec 13 '14 at 17:32
  • What UV wavelength does that process need? Hint: UV-A can be had from tanning gear and blacklights. For UV-C, I was nearly suggesting to look into EPROM erasers and germicidal lamps. However, LOOKING INTO them is exactly what you need to avoid with these, be careful. – rackandboneman May 6 at 7:55
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No, there's no conversion for LCDs — and you wouldn't have anything approaching the resolution you'd want for a print that size anyway using a digital projector.

The usual procedure for making alternative process prints from digital files is to print a negative on transparency film. It's the go-to method for cyanotypes, as well as for platinum/palladium and so on, and the results can be indistinguishable from film. The problem here is that you want to go big — really big — and that isn't going to be cheap.

Methods that print out during exposure need very dense negatives. For that reason, you need a transparency film that can hold rather a lot of ink and produce a good Dmax. The film of choice these days seems to be Pictorico, which is available in 24" x 66' rolls. (Do I need to mention that you'll also need access to a printer that has a carriage width of at least 24", like the Epson 7X00 series?)

Black ink alone will not provide enough density; you'll need a secondary UV-blocking ink laid down as well (which means mucking around a bit in your printer settings — or getting your negatives' printer to muck around a bit in their settings). With Epsons, yellow is a good secondary. You'll also need a light stochastic noise pattern added to your image's negative in order to get enough dither for contact printing. As for the printing itself, you can build a UV source, borrow some time at a shop that still does real blueprints or screen printing, or, if all else fails, use the sun. (These exposures are long, and you can inspect them under room light safely to see if they're cooked yet. Unlike platinum/palladium, the cyanotype prints themselves aren't so expensive that you can't afford the learning curve. And the weather people will give you the UV index, which will help gauge the starting time.)

There is a much more in-depth article on creating the negative by Carl Weese at TheOnlinePhotographer.com. The negative you will need for a cyanotype is very similar to the one you'd need for Pt/Pd, and you'll need to do just as much fiddling around to find the right density and curves. Remember that you can climb the ol' learning curve using standard-issue letter-sized OHP transparencies; there's no need to spring for a roll of specialty material until you're ready to rock. Just make sure that you're using the same brand and type as the roll. (It's not something you can pick up at your local business supply depot, but it's not hard to find online either.)

Do note that you would really need to make a full-sized negative for contact printing no matter how you choose to go about this (unless you can use a modulated scanning high-power UV laser). Using a projector with anything like a reasonable-sized (read "cheap") negative would mean hours rather than minutes of exposure time, and you won't be able to tell whether or not the image is in focus until it is partially printed out.

  • Wow, you've really thought this through. Thanks. And welcome to photo.stackexchange! Please fill your your profile, we need more people like you! – Paul Cezanne Dec 13 '14 at 1:35
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    @PaulCezanne - I don't want to break his cover... but he is a veteran of the site. One of the most knowledgeable ones around certainly. I hope he is back for a while, but I am guessing your question was simply too intriguing that he just had to answer! Hopefully I'm wrong :-P – dpollitt Dec 13 '14 at 4:23
  • too cool! love the mystery.. – Paul Cezanne Dec 13 '14 at 16:09
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I've done it before and it works. I used a AAXA 720p portable projector on cyanotype paper. The resolution isn't great, but maybe it's good enough for your purposes.

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I know this is an old question but I've been experimenting with this.

Projectors WILL expose cyanotype paper - I've been using 'nature print' paper. With an additional lens to get the focusing distance down (an old photographic enlarger lens and also a cheap a4 plastic fresnel - they turn out to have the same focal length) I can get a good image on an A6 sheet with 60-120s exposures - the additional lens focuses the full frame of the projector onto the sheet. This was a Panasonic pt-p1sdea projector.

I've also tried white led spotlights (12v 1a) they work for a contact print in about 5 mins.

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Try the LED projector. People are always saying "it won't work" rather than trying it themselves. You never know. It's a pretty cheap process so there's not much to lose, and for the record LED does emit UV light. Is it enough? Find out. I have a Vivibright GP100 that, at 3200 lumens, produces some amazing detail for about $150. I'm pretty sure it would make a canvas-sized cyanotype in a reasonable amount of time. If not, I've wasted $10.

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white led spectrum does not contain uv so it's a waste of money and time

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