Those like me who uses an ATI card, you should look into the driver settings in the CCC by Scaling Options and set the value to 0.
Without this option, I had on the television a black border and the Full HD resolution has been scaled down to these smaller screen area and thus did not look very sharp. CCC: Graphics> Desktops & Displays> bottom left all screens will now be displayed as icons. Choose Right-click on the TV and "Confiure ...". There are the "Scaling Options" hidden.