|This is the original 5 stop tonal range.
Nearly everything is beneath the mid-tones (green), which are minimal.
And there is a vast sky of highlights.
I'm getting more and more confused about changing from colour to b&w with
Dan's recommendation of channel blending, when one has to blend and curve
different channels in 'normal' mode before switching to Luminosity.
I think we can slightly improve the far mountains by applying the Red (or Green)
channel into the Blue in Darken mode - so I'll do that and then de-saturate -
giving this image, which is a very slight improvement (not really worth writing