twopointeight
Well-known
Can I use a Leica UV/IR 39mm filter, leftover from my M8 days, on a Fuji lens and expect it to be completely neutral, like a UV lens with no IR?
Scrambler
Well-known
Yes
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twopointeight
Well-known
perfect, done, thanks!
A bit late to the party...
My answer is "yes, but..."
And the quibble is related to the angle of the light passing through the filter. UV/IR Cut filters, while reflecting away the IR, also reflect a little of the visible red spectrum, and this is seen with the "red searchlight" effect of red light reflecting off the filter.
So there's very slightly less visible red passing through the filter, not noticeable in the center of the image. Or even at the edges with tele lenses in which the light passes through pretty straight.
But... when the light that is imaged on the sensor/film passes through the filter at a steeper angle, as with wide-angle lenses, there is more red blocked toward the edges and corners than at center. So there can be a slight cyan tinge in the peripheral areas.
One might suggest this effect is caused by the IR filtering action of the sensor cover glass, and I expect that's a small contributing factor. But it's easy enough to test for oneself. I see slightly cyan tinted edges and corners on an M240 with 28 Summicron with UV/IR filter mounted... but not with the filter removed. And also not with a 50mm either with filter or without, where the effect is too little to notice.
Confirming this result... I found the same slight cyan effect with a UV/IR Cut filter on the 35mm Summarit-S (28mm equivalent) on a Leica S2, but not with the same filter on the normal 70mm Summarit-S.
Nevertheless, I prefer to use a Cut filter with the M9 and M240 just as with the M8, and for the same reason, even if it means adjusting the tinted corners in post-processing, such as with CornerFix or the Lightroom flat-field plugin.
My answer is "yes, but..."
And the quibble is related to the angle of the light passing through the filter. UV/IR Cut filters, while reflecting away the IR, also reflect a little of the visible red spectrum, and this is seen with the "red searchlight" effect of red light reflecting off the filter.
So there's very slightly less visible red passing through the filter, not noticeable in the center of the image. Or even at the edges with tele lenses in which the light passes through pretty straight.
But... when the light that is imaged on the sensor/film passes through the filter at a steeper angle, as with wide-angle lenses, there is more red blocked toward the edges and corners than at center. So there can be a slight cyan tinge in the peripheral areas.
One might suggest this effect is caused by the IR filtering action of the sensor cover glass, and I expect that's a small contributing factor. But it's easy enough to test for oneself. I see slightly cyan tinted edges and corners on an M240 with 28 Summicron with UV/IR filter mounted... but not with the filter removed. And also not with a 50mm either with filter or without, where the effect is too little to notice.
Confirming this result... I found the same slight cyan effect with a UV/IR Cut filter on the 35mm Summarit-S (28mm equivalent) on a Leica S2, but not with the same filter on the normal 70mm Summarit-S.
Nevertheless, I prefer to use a Cut filter with the M9 and M240 just as with the M8, and for the same reason, even if it means adjusting the tinted corners in post-processing, such as with CornerFix or the Lightroom flat-field plugin.