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UltravioletPhotography

Clear UV-Blocking filters aren't really uv-blocking filters...


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I have several UV filters (the clear ones you can see through), however when I shine a 365nm UV LED through them, I can still see the light coming through the other side when looking in live-view mode on my full spectrum D7000 camera with a Baader-U filter on the CoastalOpt UV-VIS-IR lens, as if the filter wasn't even there. They should stop advertising the filter as a "UV" filter and just call it a clear filter.

 

In any case, are there any filters that DO block UV-only? Has anyone used these for their photography before?

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enricosavazzi

Many of the cheap "UV filters" do not block UVA. Some of these non-blocking filters are more honestly identified as "protector" filters, i.e. meant only to prevent accidental damage to the front element of the lens.

 

There may be UV-cut, VIS- and NIR-pass filters, but I am not able to recommend any.

 

In general, with a multispectral camera one needs to isolate the UV, VIS and NIR bands, and for this purpose a VIS-pass, NUV- and NIR-cut filter is more useful. I have used with success both the B+W 486 and the Baader UV- and IR-cut. They are similar but not identical. Some users recommend one over the other, but opinions vary. There are also third-party filters with similar characteristics, but I have not tested them. These are not transparent filters. All these VIS-only filters I have seen have a distinct greenish/bluish tinge and require a custom white balance.

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Not all UV blocking filters have the same cut-off and they do pass UV.

This is an old but general introduction to the problem

http://www.bobatkins.com/photography/technical/filters.html

Also take note that the 365nm LED is not a narrow band source and can often "reach out" into the visible.

 

If you are looking for a cheap UV (only) blocking filter you could try the obsolete (ebay) Kodak 2 gel filter series.i.e. 2A, 2B, 2C and 2E.

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The typical "UV filters" are a leftover from film days. The purpose was to block some UV in order to avoid the distant hazy look in landscapes.
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The old type "UV" filters have a quite gradual cut-off starting around 390-400 nm and might only cut 1-3 stops around 350 nm. So no wonder it didn't make much difference through your camera.
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