Modern cinemas are now highly automated and few would ever have a need to run nitrate film. The need to do changeovers has been effectively superseded with the introduction of continuous loop projection systems. These systems operate by having all the reels of film for the entire showing, main feature, supporting film, trailers etc all stuck together in one gigantic reel that is normally mounted horizontally and the film is fed from the centre of the spool to the projector where it is screened and then wound back on the outside of the same horizontal spool. Quite often these spools will be located some way from the projector and the film path may be over rollers along the ceiling of the projection room and surrounds. The lenses of the projector can be automatically rotated in front of the projector light aperture to accommodate the correct lens for a given format. The picture to the right shows a semi-automatic system using vertical spools that can hold an entire movie, however these are not the continuous loop projection systems and the film will need to be rewound after the screening. Also the rotating lens turret can be seen on the projector to the right of the image. Both of the automated methods of screening need very few staff in very often one projectionist will look after the screening of three or four auditoria in one cinema complex. Although there is no longer a need for the shutter or the small porthole like windows in the projection room they are still installed, mainly to reduce ambient light in the projection room reaching the screen.
