UV bulb in enlarger?

[Dr Klaus Schmitt]

I had been contacted a few years ago about such a solution for LF negatives using high powered 365nm UV LEDs in the enlarger head, but after some calculations decided to not go that way...

[Dr Klaus Schmitt]

I've been experimenting with UV light in an old Prinz 500 enlarger for a week. The results are promising. It works.

I shoot with antique cameras and usually make contact cyanotype prints. I wanted to enlarge without a separate digital negative process. I also started using a 35mm half frame camera (Universal Mercury II) and wanted to enlarge the half frames onto cyanotype. While it does take time for enough UV to pass through the glass optics, the only issue is the amount of time. Early tests required 5hr exposures with a 20w LED bulb.

I probably wouldn't have tried but for the lengthy explanations of why it couldn't be done!

I had been contacted about that a while ago, made some calculations and came out with several hours of needed exposure, so dropped that plan then.
Thanks for the confirmation!

[Tin Can]

Klaus, thank you for your considered views and experiments

Some are lax on Copyright

Quoting sources IS a problem as few were taught to do that

[Dr Klaus Schmitt]

Klaus, thank you for your considered views and experiments

Some are lax on Copyright

Quoting sources IS a problem as few were taught to do that

I'm admin in a large photo forum, there I would be issuing a 1st warning, 2nd would be removal of the poster ;-)

[Dr Klaus Schmitt]

Well, about the topic: today things ahev changes a bit, as high powered 365nm UV LEDs have gotten much cheaper and using some in a suitable condensor head would bring down exposure times considerably - IF and only IF a suitable UV passing lens would be used. THAT still is quite a challenge still, as many do not work. A suitable triplet lens with single or no coating would do, but would have to be stopped down - AND there is the focusing issue as those leses have considerable focus shift.

One would have to use some paper with fluorescent paint to focus on, then replace that with the photo sensitive paper and do teh exposure...

[Pere Casals]

Which glass? Don't contact print frames use glass too?

http://photographyoftheinvisibleworl...6_archive.html


Coatings sometimes block UV, so depending on the lens version a difference may be there.


Probably a condenser type enlarger may be better for UV LEDs, as difusser type are way less efficient.

[Tin Can]

Very interesting and thank you for posting

Your links will be explored, over time

Well, about the topic: today things ahev changes a bit, as high powered 365nm UV LEDs have gotten much cheaper and using some in a suitable condensor head would bring down exposure times considerably - IF and only IF a suitable UV passing lens would be used. THAT still is quite a challenge still, as many do not work. A suitable triplet lens with single or no coating would do, but
woudl have to be stopped down - AND there is the focusing issue as those leses have considerable focus shift.

One would have to use some paper with fluorescent paint to focus on, then replace that with the photo sensitive paper and do teh exposure...

[Dr Klaus Schmitt]

http://photographyoftheinvisibleworl...6_archive.html


Coatings sometimes block UV, so depending on the lens version a difference may be there.


Probably a condenser type enlarger may be better for UV LEDs, as difusser type are way less efficient.

Yes, but that used rather thin glass in contact frames transmits UV rather well, still

[ic-racer]

One of the biggest hassles in alt processes is making a full-size positive

I thought that was the easy part. I made some big negatives but gave up trying to make the platinum paper work right and went back to commercially produced silver paper.

[bnxvs]

If you use my work from my site which clearly states "All text and images carry my copyright and I do not allow to link to or copy / download from my site or any parts thereof without my prior permission." then AT LEAST quote my copyright!!

Where on this picture is indicated that it is not to be copied, cited, or otherwise used? Given that I found it in Google and I have no idea about your site - file a claim with Google. Or close your site from indexing by search engines.
And there is no need to scream like that - excessive emotions negatively affect health )))