Screen Brightness: Sony Vaio

[Rich Shepard]

   We have a Sony Vaio running Slackware-14.0/x86_64 and the Fn-F5 button has no effect
on screen brightness. I rummaged around in the Settings -> Settings Editor
-> Display dialog box and changed the screen brightness from the default 12
to 6. After rebooting there's no difference.

   What am I missing here? A pointer on how to make the screen dimmer will be
much appreciated.

Thanks in advance and happy holidays to all,

Rich