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07-08-2021, 05:28 PM   #1
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UV glass can oxidize?

Bought a full spectrum modified Pentax K-01 and have been reading up on UV photography. The Kolari website had this interesting statement: "Uncoated UV glass is sensitive to oxidation when exposed to humidity, ruining the filter". Didn't know glass could oxidize. Very interesting. UV photography seems much more complicated than IR. Very few lenses pass UV light.

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barondla

07-08-2021, 06:23 PM - 1 Like   #2
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QuoteOriginally posted by barondla Quote
Bought a full spectrum modified Pentax K-01 and have been reading up on UV photography. The Kolari website had this interesting statement: "Uncoated UV glass is sensitive to oxidation when exposed to humidity, ruining the filter". Didn't know glass could oxidize. Very interesting. UV photography seems much more complicated than IR. Very few lenses pass UV light.

Thanks,
barondla
But does it happen fast enough to really matter?
07-09-2021, 01:47 AM - 1 Like   #3
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QuoteOriginally posted by ramseybuckeye Quote
But does it happen fast enough to really matter?
well , we live longer and longer so perhaps YES.
07-09-2021, 05:01 AM - 1 Like   #4
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Most UV is blocked by optical glass. Science cameras for UV tend to have fused silica windows, often with dielectric coatings for the pass-band. eg. 150nm to 400nm.

07-09-2021, 09:08 AM - 2 Likes   #5
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QuoteOriginally posted by ProfessorBuzz Quote
Most UV is blocked by optical glass. Science cameras for UV tend to have fused silica windows, often with dielectric coatings for the pass-band. eg. 150nm to 400nm.
This ^ ^ ^

The glass is special and being special requires special treatment.


Steve
07-09-2021, 10:12 PM - 1 Like   #6
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Pentax needs to make more "ultra achromatic" lenses.
07-13-2021, 09:47 AM - 1 Like   #7
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QuoteOriginally posted by pentaxus Quote
Pentax needs to make more "ultra achromatic" lenses.
That would be termed an apochromatic lens. And most are very well colour corrected.

07-15-2021, 08:35 AM - 1 Like   #8
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It depends on what "UV glass" refers to. There are many kinds of optical glass which are adversely affected by moisture. As you mentioned, many "glasses" won't transmit UV light and some that do fall into this category (quartz doesn't). Bottom line, many glasses which can be used for UV are not affected by the environment and only a few are.

A bigger issue with UV photography is getting a lens to focus at UV wavelengths for infinity use. You can't rack most lenses close enough to the sensor to bring an infinity image into focus. This is because UV light focuses to a point in a shorter distance than say green or red light.

The UV we're talking about for full-spectrum cameras is not that far removed from deep blue, and can be passed by many glasses (it's in the range of black light for poster use). If you're trying to take a photo using this wavelength, having a color corrected lens is irrelevant since we're only dealing with a narrow range of wavelengths although a color corrected lens may have less a problem with the infinity focus issue. As you get further into the UV end of the spectrum, lens transmission does become an issue. Deep UV (vacuum UV) won't transmit through air but a full spectrum camera just doesn't go there.

It boils down to trying various lenses at the UV wavelengths you want to capture and seeing how well they do (or finding UV transmissibility data for them before considering a lens). With most, corrosion is an issue you won't have to consider. Lastly, you can use a pinhole for a lens, and it will transmit all UV wavelengths though with significant IQ issues. Any lens designed specifically for UV will cost $$$$$$.
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