Comment 39 for bug 1241745

peddanet (peter-wein), as per NVIDIA, the scope of this report was determined to be hardware dependent:
https://devtalk.nvidia.com/default/topic/539462/linux/-nvidia-319-12-brightness-controls-not-working-on-laptop-ubuntu-13-03-/5

Hence, if you would like your problem addressed, it will help immensely if you use the computer the problem is reproducible with, file a new report with Ubuntu by first ensuring the package xdiagnose is installed, and click the Yes button for attaching additional debugging information after running the following from a terminal:
ubuntu-bug xorg

Also, please feel free to subscribe me to it.