This article is from the rec.arts.movies.tech FAQ, by Scott E. Norwood snorwood@nyx.nyx.net with numerous contributions by others.
Soon after super 8mm displaced regular 8mm as the standard home-movie
format, people began to demand sound capabilities for their cameras
and projectors. The easiest way to record sound while shooting is to
record the sound within the camera on a magnetic stripe pre-applied to
the edge of the film, in the same manner as the various regular 8mm
systems. A `balance stripe' is also applied on the sprocket-hole edge,
but not usually used for sound; its purpose is to maintain an even
film thickness. Aside from having two differing frame rates (18 fps
and 24 fps), this method became standardized for both cameras and
projectors, with a standard sync offset. Sound quality is potentially
quite good, with some recording devices and projectors offering stereo
reproduction by recording twin soundtracks, one on the `balance
stripe' and one on the regular sound stripe.
The primary disadvantage to this system of recording sound in the
camera is that it makes good editing extremely difficult. Super 8mm is
usually shot with reversal film (see below), meaning that the camera
original is edited and then projected. In this case, after every
splice, there will be a delay of about one second between when the
picture edit shows up on the screen, and when the sound edit is heard;
this is a result of the sync offset of the soundtrack. For this
reason, professional films (except old television news films) almost
never record sound within the camera, but rather use a `double-system'
method, in which the sound and picture are kept on separate strips of
film through the editing process, until the final release prints are
made. Home movies, though, rarely undergo substantial editing; thus,
`single-system' sound recorded in camera is useful and convenient.
 
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