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Photochromic lenses and visors
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Will photochromic lenses work behind a normal visor? I was considering
getting some but my optician informs me they don't work very well inside
cars and might well have similar problems in a helmet.
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If I'm remembering my physics correctly, glass absorbs UV light, but most
plastics don't (at least not so much). So if the lenses are reacting to UV,
they should work better through a plastic visor than a glass windscreen.
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Windscreens have a plastic layer between the two glass panes though.
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Don't know how you work that out, eg:
Polycarbonate lenses, 99.9% UV Protection.
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And you think that UV protection is purely down to the fact it's made from
polycarbonate, do you?
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Eh?
You said most plastics don't absorb (much) UV. I gave you an example of
a plastic which, apparently, does.
Ergo, I'm right, you're wrong. Hurrah.
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No - I'm right in saying that *if I remember my physics correctly* glass
absorbs UV light,
but most plastics don't (at least not so much).
Evidently I don't remember correctly. My statement's still right though. And
polycarbonate isn't 'most plastics', so you're wrong. Nerr nerr ne nerr
nerr.
Anyway - I've done my research now, and it turns out that it's glass that
absorbs the least UV. Most plastics are not 100% UV resistant, and require a
coating to make them so. Polycarbonate is inherently 100% UV resistant
without treatment. This is a good summary:
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Mine do. As long as your visor doesn't block UV, you'll be fine.
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Mine work as well in a helmet as they do outside.
It seems to be impossible to get photochromic lenses that go dark enough.
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That's always been my main objection.
He did show me some nice frames with magnetic clip-on sunglasses, which
looked quite good. A bit pricy, though, compared to the tat I usually buy.
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My first pair, in 1979, was OK but there are just pale imitations nowadays.
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Mine work in both the car and the lid.
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