The actors stand in front of a screen while a projector positioned behind the screen casts a reversed image of the background. This required a large space, as the projector had to be placed some distance from the back of the screen. Frequently the background image would appear faint and washed out compared to the foreground. The image that is projected can be still or moving, but is always called the "plate." One might hear the command "Roll plate," to instruct stage crew to begin projecting.