Color Zones for Monochrome

I used the darktable Color Zone module on this ghostly image.

Color Zones > switch to black & white > saturation mode > pick the ‘blue’ from the sky > change to lightness mode > reduce the blue from the sky to zero > pick the building color > bring up building color lightness to full

Also tried the (or better had to use) the spot removal module for the dirty sensor.

Fun to play!

Dark RAW