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Old 9th July 2018
Petrochemist Petrochemist is offline
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Re: m4/3 lenses for IR

Quote:
Originally Posted by MikeOxon View Post
The glass types used for making most photographic lenses are, themselves, pretty opaque to UV. I've never really understood the need for a special filter, unless its cut-off extends into the short wavelength end of the visible spectrum, to reduce a blue cast in snow scenes.


I've started some experiments with the Schott WG and GG filters and will report on the results in another thread.

I've measured the spectral transmission for some of my lenses. Yes the modern MFT lenses transmit very little UV, and even reduce IR by a surprising amount. The lens I used for my trials was a El Nikkor 80mm enlarger lens that does transmit a reasonable amount of UV.
My lens data may not be very readable on-line but it summarized here


There's a similar set for some of my filters as well here though you can download data on schott glass from many suppliers such as UQG outside Cambridge. I have a GG495 somewhere, and must have tried it once or twice but I don't think I have any other WG or GG grades.

I think my best results with schott glass have been with BG3 & U330 or U340 filters which give UV, blue & NIR in various combinations. Quite a few old photographic filters work well for IR on converted bodies
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