My laptop is over a year old now and after I installed windows 10 it would never have these issues. On every startup the brightness gets really high and the brightness controls become inverted even the new power saving mode makes the brightness brighter. I fix this by just putting my laptop to sleep again and turning it back on. It returns to normal but this happens everytime on starting up from shutdown, starting up from a long sleep, and restarting. Restarting also has a issue where sometimes my laptop will be stuck at a black screen. If this is an issue with my hardware then I guess I'm just going to have to live with this.