Twilight and Lux both contain naive implementations using a semitransparent overlay. The result of this that blacks and dark colors end up being brightened instead of left alone, as a proper color-temperature change would do. This looks bad on all screens, but especially so on AMOLED displays that support a true black.

Cf.lumen[1] is, I believe, the only Android app that can actually change the color temperature of the screen like f.lux can, but it requires root as well as installation of a special "driver" in order to do so. My guess would be that the "complicated install process" referenced by the f.lux devs is probably similar.

[1] https://play.google.com/store/apps/details?id=eu.chainfire.l...

For reference, the most popular screen dimming/warming apps for Android:

- Lux (free/$3.80): https://play.google.com/store/apps/details?id=com.vito.lux

- Twilight (free/$2.99): https://play.google.com/store/apps/details?id=com.urbandroid...

I have no idea. But the developers (of f.lux) seem to claim elsewhere that the existing solutions aren't 'solutions' at all; don't do it properly.

I can't speak for the truth of that though. I've used the aptly named "Blue Light Filter" which seems to work fine. CyanogenMod OS bundles something which seems okay too.

Twilight doesn't properly dim the whole screen, it leave the menu bar undimmed and is good but not great.

CyanogenMod also has a very nice feature which adjusts the colour cast of the screen based on both time of day and the colour of the light hitting the RGB sensor.