These so-called "process shots" were widely used to film actors as if they were inside a moving vehicle, who were, in reality, in a vehicle mock-up on a sound stage. In these cases the motion of the backdrop film and foreground actors and props were often different due to the lack of camera stabilizing in the filming from the moving vehicles used to produce the plate. This was most noticeable as bumps and jarring motions of the background image that would not be duplicated by the actors.