In the kinetoscope the films passed by continuously.

The time of the exposure through the opening in the revolving shutter had to be extremely short in order to give distinct pictures.

The slightest lengthening would make the movement of the film itself visible and produce a blurring effect.

This time was sufficient for the seeing of the picture; it could not be sufficient for the greatly enlarged view on the wall.

Too little light passed through to give a distinct image.
Hence it became essential to transform the continuous movement of the film into an intermittent one.