After the installation of Windows 8.1, I had noticed  that the brightness of the laptop went down considerably low. Even by increasing or decreasing the brightness (F11 and F12) situation did not improve. The solution is a simple one. One just needs to re-install the graphic drivers and upgrade the Lenovo power management.

• Intel Video Driver for Windows 8.1(32-bit  or  64-bit)
• Nvidia Video Driver for Windows 8.1(32-bit  or  64-bit)
• Lenovo Power Management for Windows 8.1(32-bit, 64-bit)

Alternatively one can simply visit the official forums of Lenovo about this particular issue.