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Laser scan lenses for UV?

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#1 Stefano

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Posted 04 June 2021 - 16:54

I am searching a lot on eBay these days hoping to find interesting stuff. I found these UV laser scan lenses, I don't know if they are any good for UV photography. Quite expensive for me.

Here's two:
https://www.ebay.fr/itm/254985169572
https://www.ebay.com/itm/124635178395

#2 Andrea B.

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Posted 04 June 2021 - 19:10

I tried to google for use of f-theta lenses for photography but found nothing - so far.

One thing I have observed is that the working distances (for scanning) are quite large and some must be added to that to obtain the flange focal distance. Looking at JenOptik's 355 nm f-theta lenses, I saw that the minimum working distance is 60 mm. Other example working distances are 135 mm, 182mm and larger.
So you would have to put quite a long extension on the lens to adapt it to a Sony, Nikon Z or m4/3 FFD. Nikon, Pentax, Canon DSLRs already have at least 40+ mm in their FFD, so such a lens might be more adaptable to a DSLR than to a mirrorless.
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#3 nfoto

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Posted 04 June 2021 - 19:20

These lenses are likely designed for a very narrow passband. I have a Rodenstock f-theta lens somewhere that delived "rain-bow" coloured images all over due to the manner in which it did (or rather, did not) handle chromaticity.

#4 Stefano

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Posted 04 June 2021 - 19:22

What I wonder is if they have a good image quality and if their reach goes deep. But a lens optimized for 355 nm probably doesn't reach UVB.

Edit: I posted this before reading Birna's post.

Edited by Stefano, 04 June 2021 - 19:23.


#5 Andy Perrin

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Posted 04 June 2021 - 19:55

When you need to have antireflection coating for only a single wavelength, you can use a 1/4 wavelength single layer coating. It will cancel the reflection at just that single wavelength. However, that implies that for any incoming light at half the design wavelength, it becomes a perfect mirror... :grin:

(And this, of course, is what leads to the idea of multilayer coatings.)

Edited by Andy Perrin, 04 June 2021 - 20:00.


#6 Andrea B.

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Posted 04 June 2021 - 19:58

So forget about f-theta lenses for general reflected UV photography !
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#7 Andy Perrin

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Posted 04 June 2021 - 20:08

View PostAndrea B., on 04 June 2021 - 19:58, said:

So forget about f-theta lenses for general reflected UV photography !
Emphatically so. It might be okay if you paired it with a very narrow bandpass filter at the exact wavelength of interest. Not sure why you'd want a lens/filter combo that only works at a single wavelength, but perhaps someone around here might dream up a future use for such a thing.

#8 Stefano

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Posted 04 June 2021 - 20:29

I didn't find such lenses made for wavelengths below 355 nm. Having one optimized for a UVB band in the low 300s and a narrow bandpass filter may be useful to some. But that would be limited to that specific wavelength.