Tried the
camp demo, still think 25% luminance reduction and 75% saturation looks best. On the tents in the dark it's hard to choose between 25/75 and 50/50 though. I felt like 25/75 left the red tent a bit too bright, and 50/50 darkened it a bit too much. 33.3/66.7 might be a good compromise for that particular scene. 100/0 is right out by the way, causes awful banding on the sun at the beginning of the scene.
Edit: Oh, I should mention I tested this using 120 nits for the display luminance to match my calibration, but 120 nits might still be overbrightening things. 180 nits looks less washed out, though it's hard to say what the 'right' brightness should be.