I am unable to change the brightness of my Acer Aspire V3-571-6850 laptop.
My system details are:
Memory: 7.6 GiB Processor: Intel Core i5-3210M CPU @ 2.50Ghz * 4 Graphics: Intel Ivybridge Mobile OS type: 64-bit Disk: 730.0GB
You can change brightness using command line as follows:
For more information, refer to this backlight Wiki.
You may need to install proprietary drivers for your graphics card.
[EDIT: additional information on Intel Graphics]
Intel graphics drivers for Ubuntu 13.04 have recently been packaged and released by Intel in an Ubuntu installer:
I can't vouch for how well they work, since I don't have an Intel graphics card, so just be sure you follow the instructions and be aware of any "Known Issues" that are presented on the package website.