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I realise that, but the blue

I realise that, but the blue channel will not be proportionately affected. A mix of CCR and CCM would be needed to equalise the balance, just wondered in view of the serious effect of red channel noise on blue skies whether CCR might not be a better option.

Some time ago (2-3 years) I did some tests using 80B filters for tungsten, and found that between 1 and 1.5 stops of highlight headroom was recovered by shooting with 80B (based on ACR conversions of the time, KM 7D). Iliah's findings show that maybe ACR was pre-boosting the red channel anyway. A different filter (not 80B) might have enabled equal channel gain in raw conversion. I worked in the 1990s with Leaf and other scanning backs, researching hot mirror filters and light balance filters to recover better colour information.

It surprises me that this kind of work (I'm just a photographer, my wife is a colour scientist) does not seem to have influenced the design of RGB filters for Bayer-type sensors. The sensor itself, unfiltered, is highly sensitive to red. But gradation in the red channel is determined by the blue component more than any other. The work of Dr Andrew Stevens in the early 1990s has also been ignored - he showed very effectively how only two coloured filters were required to produce full colour, not three. Andrew was a colour scientist with Kodak but I don't know where he is now. He was able to produce pseudo-isocolour from a panchromatic film and an orange filter, plus an exposure level - nothing more needed (two exposures)!