Samsung UN46ES7500F E-Manual page 215

may take some time until the 3D display is
optimized.
ΠThe 3D Active Glasses may not work
properly if there is any other 3D product
or electronic devices turned on near the
glasses or TV. If there is a problem, keep
other electronic devices as far away as
possible from the 3D Active Glasses.
ΠBe sure to stay within the viewing angle
and optimum TV viewing 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