Brightness adjustment keys have no effect (although they are recognized by the environment), and I can't change the brightness using GUI tools as well. In Windows 10 i had the same problem and after i changed my driver into those for windows 8 i could fix it.
Output of "sudo lshw -C video":
*-display               
       description: 3D controller
       product: GK208M [GeForce GT 740M]
       vendor: NVIDIA Corporation
       physical id: 0
       bus info: pci@0000:01:00.0
       version: a1
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list
       configuration: driver=nvidia latency=0
       resources: irq:32 memory:d2000000-d2ffffff memory:c0000000-cfffffff memory:d0000000-d1ffffff ioport:3000(size=128)
  *-display
       description: VGA compatible controller
       product: 3rd Gen Core processor Graphics Controller
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 09
       width: 64 bits
       clock: 33MHz
       capabilities: msi pm vga_controller bus_master cap_list rom
       configuration: driver=i915 latency=0
       resources: irq:28 memory:d3000000-d33fffff memory:e0000000-efffffff ioport:4000(size=64)
I use the property driver of Nvidia instead of Noveaou
Output of "ls /sys/class/backlight/*/brightness":
/sys/class/backlight/intel_backlight/brightness
I've yet try to resolve the problem follow this:
Screen brightness isn't taking effect on a Lenovo Z570
but this haven't working for me.
How Can i fix it? Thank you!!! :)
 
     
    