You'd think that everything that is projected to the screen all the way out to the
edges should be displayed on your TV. Well, not really. The edges would have
fringes that would be annoying if not unpleasant to see. So what do you do?
You "zoom" in on the picture so that the edges disappear into the edges of your
screen. This is what overscan is for. It is like looking through the camera,
the more you zoom in, the more you filter out or lose objects in the periphery.
Here is a graphical description of overscan. Graphic is not to scale.
0% overscan is the edge of your screen
3% overscan is the blue area. The blue mask (area covered by the
blue borders) indicate the area of the picture that will be lost.
5% overscan is the red area. The red mask indicate the area of the
picture that will be lost. Incidentally, the red area is overlaid over the blue
area. Hence, the 5% overscan fully covers the 3% overscan area as depicted
above. This appears to be the overscan for most convergence grids.
Again, the image above is not to scale. It was exaggerated for
illustration purposes only. So, you don't really lose as much of the picture the way
it is represented above.
Ways to correct overscan
Entering the tv set service menu and adjusting parameters that affect horizontal and
vertical size. Related also are the horizontal or vertical position, if adjustments
are needed.
Entering the service menu and working on the convergence grid, or
Using an htpc to control the image size without ever having to enter the service menu.
