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K0CQ > LIGHT 13.12.05 08:41l 33 Lines 1595 Bytes #999 (0) @ WW
BID : 16054_W0AK
Read: GUEST HA1SE
Subj: Re: infra red and beyond ?
Path: DB0FHN<DB0FOR<DB0MRW<OK0PPL<DB0RES<DK0WUE<7M3TJZ<CX2SA<VE2RXY<VK7AX<
VK2TGB<VK2IO<VK2WI<VK2AAB<N7QDN<N0RVX<W0AK
Sent: 051210/1948Z @:W0AK.#CIA.IA.USA.NOAM #:16054 [Des Moines] $:16054_W0AK
From: K0CQ@W0AK.#CIA.IA.USA.NOAM
To : LIGHT@WW
> hi all , a question for all you tecky bods out there , is it possible to
> get / make some sort of variable filter to enable a already infra red
> equipped video camera - " see " further into the infra red - ultra violet
> range of light frequencies ??
Generally the IR and UV limits are determined by the response of
the sensor and the transmission curves of the lenses. Ordinary
glass doesn't pass IR very far from visible, nor UV. Takes
special lenses for longer IR, sometimes made of germanium but
that looses their visible transmission range. Takes quartz to get
very far into UV, but those two material make for other problems.
Good camera lenses are made up of glasses with different
refraction coefficients to compensate for the spectrum dependent
focusing of all practical materials, then are coated to minimize
reflections in the visible. UV and IR having different
wavelengths the coatings become ineffective or act as stop
filters.
> or conversely - I know you can get infra red film ( 35 mm ) can ultra
> violet film be had ? - i suspect though this would have a fairly narrow
> bandwidth ??
Ordinary B&W film is sensitive to UV, that's why serious
photographers always have a skylight filter (Kodak 1A) to cut
back on that UV sensitivity that tends to cause flare and excess
sensitivity at UV. That could be reversed with a filter that
passed only UV, but the lenses would limit the available results.
73, Jerry, K0CQ @ W0AK.#CIA.IA.USA
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