Screen management - turn off timer

In the power management options, I have set my laptop to tu the screen off after 10 minutes of inactivity.

The issue I am ruing into is that the backlight for the screen tus off, but the actual display does not.

Is there any way to correct this situation?

Computer :
Early 2008 MacBook 13" 2.4gHz, ruing Kubuntu 16.04. The issue existed on 15.04 as well as 15.10.

Thanks