On my Android 4.4 device, is there a way to change the auto-brightness values without rooting the device, e.g. by writing a tiny application?
It is perfectly possible or you can use one of existing solutions on Google Play (for example Lux)
EDIT: OFC it works with 4.4, using it myself.
Screen Filter changes brightness below what is possible using auto or manual settings. It works on Android 4.4. Great for bed time reading.
Correction - (and contrary to the down vote) it does let you set the Auto Brightness Level to a level below what it normally would be - without rooting. I just tested it.