How can dimmer external monitor

Hi I use an external monitor attached to my notebook with display port. I configured the powersave of my notebook and after 5 minutes the dimmer monitor work only on integrated display of notebook. How can dimmer also the external monitor?

Can you please always tell which version of openSUSE you use.

And also which desktopp (KDE, Gnome, other).

yes I use opensuse 13.1 with KDE desktop.
thank you