Samsung UA40ES6200R E-Manual page 266

distance when watching 3D pictures.
Otherwise, you may not be able to
see 3D effects properly.
ΠThe ideal 3D viewing distance is
three times or more the height of the
screen. For example, if your screen
is two feet high, you should sit at
least six feet from the screen. We
recommend sitting so that your eyes
are level with the screen.