Bias line


The exposed line of soundtrack resulting from an unmodulated signal. 1

The normal rest position of a galvanometer gives an exposed line of half the available width. During quiet passages the average position is reduced by applying a direct current signal or bias current, to the galvanometer.

This current is adjusted so that without a signal the exposed area of the negative is about 0.05mm wide.


1 Case, D., 1985, Motion Picture Film Processing, Media Manuals, Focal Press, London, Boston