Hello from Switzerland/France

[AlanBradford]

I am a photographer working in Analog and Digital with over 50 years experience of Darkroom silver gelatine work.

 

I also work in Alt Photo printing, hence the UV interest for the 365-370 nm range in particular.

 

I am looking at ways to use projection of UV light to print Platinum/Palladium print using high intensity UV LED panels, with the main difficulties being the blocking of UV by most glass lenses, and iI am particularly interested in lens constructions using Calcium fluoride or similar non blocking UV materials.

 

Hoping I can learn more about UV from your group, and hopefully find some like minded experimenters to share ideas.

 

Alan

[nfoto]

Welcome indeed to the UVP community. We appreciate the growing interest in all things UV (or outside the visible spectrum) and the proliferation of techniques is exciting to learn for all of us.

[colinbm]

Hi Alan, there is a lens sticky here with lots of 365nm capable lenses.

Can you show some of your works please ?

[Andy Perrin]

None of us are lens designers although a few people have the quartz fluorite lens elements in their lenses. There has been some experimenting with quartz singlets on the forum but nobody has tried to correct one!

[dabateman]

So far the best I have made is a 35mm and 110mm fused silica lenses with each 3 elements. The distance between the elements is critical to avoid significant chromatic aberrations, at least in visible light. Also the aperture ring control should be as close to the rear of the main group.

My 110mm has the 3 elements on front of the aperture ring. My 35mm has 2 in front and one behind.

 

You can also make a simple ball lens with a concave element in front (cave on ball) of a lens ball. Mine is a bit soft, but I like the super shallow dreamy look. Its a 50mm concave element in front of a 40mm in diameter K9 ball. It passed all light above 300nm. The lens balls are really cheap.

 

There are proper programs to calculate how best to make a lens. But I can't afford proper lenses. So I work with the cheap elements I have been able to get from Ebay. So my recent lenses are a little unusual, with mixed element sizes. But they work at 250nm and I have minimized chromatic aberrations and some spherical, but since I mostly place my subject in the center, spherical correction wasn't top priority.

[Andy Perrin]

You don't work with fluorite, though, do you David?

[dabateman]

No none of the cheap lens available have it. I have only played with Bk7 (>300nm), k9 the Chinese equivalent, PMMA plastic lens, fused silica and Chinese equivalent jgs1. I almost got a cheap Aluminum oxide (sapphire lens) but didn't win.

 

Most of the cheap stuff isn't ideal. Maybe why so cheap. So some trial and error is needed and will not fit the standard models. You should correctly measure what you get if you want to correctly build it. But part of the fun is adjustments. That what many biophysical PhDs are really all about.

 

With aperture control rings and helicoid adapters, cheap on Ebay, it probably easier now than ever to build something yourself.

 

This website will become your friend:

https://refractiveindex.info/?shelf=main&book=Al2O3&page=Malitson-o

 

Change the substance type at the top of the page with the pull downs to select anything.

[Stefano]

David, I'm really curious about your lenses. Will you start a topic about them sooner or later?

[dabateman]

Most likely not. I could show a picture though.

I found that the SvBony 0.5x focal reducer is a positive meniscus lens. You need to flip it so the concave side is facing the sensor and it works well to reduce spherical aberrations. Its most likely Bk7 as its a single element that passes light above 300nm.

 

Thorlabs sells AR coated 245nm to 400nm fused silica elements in 25mm diameter that are under $150. But thats too much for me now. If I really like one of my designs I might do it correctly with coated elements one day.

I got my elements all under $15 each. But they are uncoated.