Thread: For sale E-M5 MkI converted to IR
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Old 14th September 2018
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Re: E-M5 MkI converted to IR

Originally Posted by raichea View Post
I guess, as filters aren't perfect, the combination of 665nm and 720nm attenuates the light a little compared to a single, internal 720nm filter but, if so, the exposure meter takes care of that and I doubt it's as much as 0.5 of a stop (and I suspect a lot less than that).

Nearly all the long pass IR filters I've looked at transmit at least 90% from around 20nm above their listed cut off. So the usual loss would be around 5% (1/10 stop). I think the only exception has been the 950nm which has a much more gradual transition, taking hundreds of nm to go from blocking to full transmission. Combining a 950 with an 850 would possibly show some differences in careful testing. Combinations of the other standard IR filters (excluding the 950) will produce results that would be very hard to tell from the longer wavelength filter on its own.
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