Planes can be shifted by n (plane 0) or N (all planes) with directional arguments, but that just loads an appropriate rule table; s or S have to be used to do the actual shifting. There is an inconvenience that one loses the current rule table in the process, making it necessary to reload it. Sometimes one doesn't know, or has forgotten; sometimes pressing INSERT again suffices.
Shifting the planes is most useful on startup, which typically loses the origin of the bitplanes, making it desirable to center a previously existing image once again. Images can be carried over, from one session of CAMEX to another, or even from a previous usage of the AUTOMATRIX FORTH program. The principal requirement is that the computer should not have been reset nor turned off during the interim.