Quote Originally Posted by AgX View Post
An alternative way would be to stop a swing lens after exposure just off the film, thus blocking the slit. Then advance the film, and expose by means of swinging back to the initial position. Again stopping just off the film.
This would make a baffle obsolete, but at the same time the controlled swing mechanism (shutter) would need an additional revesing device.

On the other hand such a baffle, if designed as a coaxial plane as done here, enables to get an additional feature, namely control of slit-width and thus another means of controlling exposure time.