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M9 IR sensibility/reddish color cast


chrismuc

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I bought a 2nd hand M9, works nicely. 

I thought only the M8 had the problem to be sensitive to IR due to the lack of an IR filter on the sensor.

But actually my M9 records black nylon fabrics with rather red color cast.

Is that normal?

Anything can do in post?

I have the original sensor. Would the replacement glass + sensor have a more efficient IR filter?

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When the problem first appeared on the M8,  I took the photo from the internet into photoshop.    Then made a color selection of the offending place and did a desaturation.  I leave the filters on all time for M8 and M9 photos.

 

If you can not get a decent selection,  I would make a dup layer , desaturate the whole thing, then make a mask and hand paint the coat white.

 

There will be trouble separating the darker areas of the coat from her dark hair.  You might have to hand modify the mask making her hair black .

 

PS experts can suggest a better way to mask.  

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color select-  hand paint mask to deselect hair-  desaturate

 

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Simple and effective solution is to use IR cut filter on all lenses. The magenta problem is especially bad under tungsten lighting. I used to do a lot stage and theatrical work. IR cut filter is essential then. In daylight, greens are marginally improved using the IR  filters. Beware of reflections from the filter (any filter) at night when light sources are included in the image.

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If you're going to desaturate in post processing to restore the magentas to blacks then I recommend using LAB colour space instead of RGB and desaturating in the 'A' channel so that the luminosity/luminance will be unaffected.  No selection or mask needed, just Desaturation brush at 100% in PS.

 

Pete.

 

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