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UltravioletPhotography

Lens UV Damage Threshold


JCDowdy

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My off axis parabolic collimator will be delivered soon. Before I strap it onto a 40W deuterium arc lamp and see how well some of these lenses I collected really transmit, I have pause to ask a question of our more experienced members.

 

Has anyone ever heard of a lens being damaged by exposure to high levels of UV, particularly during transmittance testing?

 

There is no guidance on this in the lens transmittance standard as it is limited to longer, 350-700nm, wavelengths. I suspect lens elements cemented with UV curable adhesive might brown if subjected to high intensity short wavelengths. Vintage balsam is organic and also might "sunburn" if over exposed. I can handle the thermal loading for IR transmittance but sure would hate to spoil any lens other than one from the junk box.

 

Thanks,

John

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John,

 

I have used hours of high intensity UVA to clear the yellowing of thorium oxide lenses. The balsam cement was not adversely affected. Note to self: check Biometar for yellowing and treat if necessary.

 

Reed

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Colour centers can be created or bleached with SWUV although I can't recall any occurrence of this for photographic lens glass at 30-40W Deuterium levels. Often times discolouration is temporary and can be recovered by exposure daylight (but not always). Can you defocus the beam to reduce flux density and still perform testing? I am sure you are also aware that Canada Balsam will fluoresce as will certain glass types.

 

I would be interested to know your final test configuration setup.

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Thanks guys!

I hope to have something substantive to post soon.

I know I keep saying that but between having to earn a living and not wanting to post until I have it all correct it has been an elephant's pregnancy!

This next version will actually be the Mark-III setup!

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That earning a living stuff sure does get in the way, doesn't it? :D

 

I'm certainly looking forward to your efforts on UV transmission, JD. I would love to fly into Tennessee someday with a couple of bagfuls of UV lenses and see how this all works.

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Andrea,

 

Bagfuls of UV lenses would probably be a long vacation at the pace this is going! :D

 

That work thing does tend to distract but the used collimator seems to work fine after a little cleaning!

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