Does anyone know the relationship between the battery life and screen brightness? Like, how much faster does my battery drain if I increase brightness by two notches? Does it matter where on the spectrum those two or three notches are? Like, is it equal no matter where? Two notices up from zero will drain 5% faster for example... just like two notches up from middle will also drain 5% faster, or is a two notch increase different depending on where you are? I tried looking this up on the interwebs but couldn't find any hits.