The Light And The Dark
While surfing the web today, I came across a user with the same problem and simple shell scripts that purport to fix it.
I downloaded the scripts and reading through them I know it won't work without edits as the directory location and hardware on the laptop do not match the script.
Copy the scripts to /etc/acpi/
To increase brightness use Fn+Up arrow
To decrease birghtness use Fn+Dn arrow
I'll post scripts after making necessary changes to directory entries and hardware.
I don't have time right now.
Soon!

Hi, Did you ever find a solution to changing the brighness of your laptop monitor? I am struggling with this same problem on LXDE.