Apologize for my english. Get low brightness after each reboot? Dont worry this solution will help u.
Let me explain step by step.
1-Full to brightness firstly.
2-Open it
gedit /etc/default/grub
then find this line
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" and change to GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"
save it.
3-Type "update-grub" in terminal (without quotes)
4-Reboot your system. U will see low brightness again but here is real solution.
5-Rollback what u did. Change back to
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
6-Type "update-grub" in terminal AGAIN.
7-Reboot and Done.
