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I have read that in order to operate a "full spectrum" camera properly, so as to not block light in the ultraviolet portion of the spectrum, that one needs to acquire quartz lenses for one's camera. Is this indeed the case?

I have also seen that perhaps other lower cost options (such as perhaps plexiglass) may be an option, but I can't find anything solid with regards to the supporting data behind this.

I am considering acquiring a camera that has been modified to go down to 250nm, but I am not sure how to be certain that the camera's lenses themselves will not defeat the pre-moded effort. So depending on the answer to the first question, it begs the followup: If glass does destroy UV input, then how can one test or understand where the cutoff is for a glass lens?

  • Related lenses: UV Nikon 105mm f/4.0 (to 220nm) and Costal Optics 105mm f/4.0 (to 250nm). Its not so much that the glass doesn't pass through the light (though some is lost in transmission), but that it doesn't focus the light well. UV lenses are designed to focus the light well along with the short pass. – user13451 May 22 '15 at 20:38
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It's true that most lenses don't transmit very much UV light, however, it's not true that only quartz lenses are suitable for UV photography. You can also use enlarging lenses, and even some modern pancake lenses can work pretty well.

You can find my previous answer to a similar question, with a bit more detail here: Are there cheaper alternatives to standard UV photography equipment?

Note that if you are actually interested in capturing a full spectrum image in sunlight, then it doesn't really matter if the lens blocks UV or not. The amount of UV in sunlight compared to visible and near IR is so little it contributes virtually nothing to the image. i.e. a full spectrum image in sunlight will look the same as a Vis + IR image.

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  • In this particular case I am interested in capturing much more faint UV region radiation that is not from the sun. It has to do with energy from electrical equipment and EM radiation around that region of the spectrum. The more sensitive the better. Interesting answer and thoughts and if you have more suggestions in this vein, I'd much appreciate it! – ylluminate May 22 '15 at 20:07
  • If you need to go below 350nm - 320nm then you likely do need a Quartz lens. You might want to try contacting Klaus Schmitt (probably the most knowledgable person on UV photography) about the possibility of purchasing a 'cheap' Quartz lens: photographyoftheinvisibleworld.blogspot.de/2014/03/… Bear in mind that while the page states the lens will be made available at a 'reasonable price', I suspect this will be in comparison to other Quartz lenses. – user20622 May 27 '15 at 9:40
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I am not sure what the spectral transmission of glass is at 250nm but you can test the transmission by using a spectroradiometer. You can point the radiometer at a test light source and measure its spectral power distribution. Then place the test lens between the source and the radiometer and measure it again. Divide the two measurements to get the transmission of the lens at each wavelength. Be sure your test source has sufficient power at the wavelengths you are interested in.

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  • That is a very interesting approach. I am not sure how to get my hands on a spectroradiometer at this point though unfortunately. The only ones I've seen after doing a little digging on your input is for IR versions and may be cost prohibitive for this particular project. But nice input nonetheless! – ylluminate May 18 '15 at 18:59
  • There are a handful out there that go down to 200nm but you're right that most go to about 380nm. – agf1997 May 19 '15 at 1:44
  • Are you aware of any way to check on this without a spectroradiometer? I am curious as to whether or not there are certain bulbs or LEDs that could be used that would allow for a "visual" test. Eg, you would take a camera and then use a series of different light sources that would be at limited / specific wavelengths and then see which ones are clearly seen on the camera. – ylluminate May 19 '15 at 15:52
  • Problem is typical cameras and our eyes both don't see wavelengths in that range. – agf1997 May 19 '15 at 15:53
  • In this instance I have been in communication with the "modder" who is completely confident that this particular camera will go down to at least 280nm and probably actually 250nm. He even went so far as to say I can return the camera for full refund if I'm not satisfied (I live somewhat close and so I would actually be able to confront him in person if there was a problem, but the price is definitely to the point where it'd be worth just hanging onto the camera). – ylluminate May 19 '15 at 16:01
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From a long time back when I was looking into film astrophotography (and the hype around hyping film - never did get into it) there was a website that I can no longer find that had tests of various films and their spectral sensitivity. There are a few very important frequencies of light such as 656nm that astro-photographers are very concerned about. The 656nm line is the Ha line that is in the deep red where film is less sensitive and also the color of a lot of things in the night sky.

So, the test that was done had an array of LEDs at specific frequencies of light shining in a box that were then shining on some surface.

--- 
  |    ..
LE|D Ooo..  660nm
  |    ..
  |
  |    ...
LE|D OOoo.. 650nm
  |    ...
  |
  |   ooo..
LE|D OOOo.. 640nm
  |   ooo..
---

Pardon my poor ascii art skills there. It had three LEDs in a box with the wiring and the diode sticking out of the cardboard. The O is trying to suggest how bright the LED's light was on the photograph (all were calibrated to be the same brightness in light produced). The difference there was the performance of the film.

A similar approach could be used with UV LEDs in the range were you are interested in. I would suggest also having something that you can focus on in the scene that is illuminated by the UV light to make sure that the lens can not only transmit the UV as desired, but also properly focus it.

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  • This is very interesting and I'm going to have to chew on this a bit! FYI, if you're on a Mac, this might be fun for you in terms of enhancing your mad ASCII art skillz! :) – ylluminate May 22 '15 at 21:29
  • @ylluminate I'll draw.io it when I get back on a machine where the best browser isn't ie 10. – user13451 May 22 '15 at 21:31

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