Samsung UE40ES7000U E-Manual page 111

Zoom: Magnifies the 16:9 wide pictures
vertically to fit the screen size.
4:3: The default setting for a movie or
normal broadcasting.
N
Do not watch in 4:3 format for a long
time. Traces of borders displayed
on the left, right and centre of the
screen may cause image retention
(screen burn) which is not covered
by the warranty.
Screen Fit: Displays the full image