The actual time that exposure is allowed during the period that the camera shutter is open, is determined by two factors. The speed the shutter is open and the shutter angle. Nominally we refer to the motion picture camera shutter as being a 180 degree shutter.
Some cameras have adjustable shutters.
This is the period of time it takes a 24 frame video signal to complete the raster scanning of a single field. If the shutter is running at 24 fps and is set at other than 180 degrees, the closed period will be the compliment of the open period. A 200 degree shutter refers to 200 degrees open and 160 degrees closed. A 160 degree shutter refers to 160 degrees open and 200 degrees closed. The position of the error bar is determined by the exact shutter to field phase relationship.