Menu
Picture
Display Settings
Picture Size
...then you have few options;
Full, Theater Wide 1, 2, 3, 4:3, Native.
You also have 4:3 Stretch and Auto Aspect.
Experiment with settings, just watch the edges of steady picture, be sure you dont cut off the edges of original picrure.
I use NATIVE setting.
Don't forget to adjust the sound.
Good luck!