I'm owner of Samsung NP-N150-JP01PL.
In my case after installing samsung-backlight and samsung-tools I use following sollution with success:
1. edit /etc/default/grub
sudo nano /etc/defautl/grub
2. change line from
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"
3. update grub
4. create file /etc/modprobe.d/samsung-backlight.conf
sudo nano /etc/modprobe.d/samsung-backlight.conf
5. insert into this file following line and save it
options samsung_backlight use_sabi=0 force=1
6. reboot the system
This solution was checked under GNOME and KDE and in both it works perfectly.
Naturally you can use your favourite text editor instead of nano.
I could only set the brightness to the min or max with the backlight keys on my NF-310, I tried everything on this thread, with no success, but with your solution it finally works! Thanks!