I had a look at the 'Night Light' option in Windows 10 and I considered it so red and so dark as to be unusable, and my monitor is too bright above 40%. My problem is that if accurate colour judgment needs to be made (like outputting images or print documents), using a calibrated monitor and/or printer is essential. If the monitor's colour balance is changing in real-time (as that seems to be what f-lux is offering), whilst maybe great for general reading it would be a nightmare for reliable proofing and output. Unless I'm missing something important?