Todays films are spliced together and run from a reel which is layed horizontal to the projector. This one reel is the entire film. No projectionist needed. More on that later.
In comparison to the system from before where reels needed to be changed every 15 minutes.
When the New Vic opened in 1930 it had 3 projectors. There where the two main units and a third constantly on standby in case of breakdown.
The projectionists job was to check, load and keep the film in focus. Changing of the reels meant watching the film, watching for the circular flash that appears in the top right hand corner. This flash was the signal to start projector number two. Then on seeing the second flash, projector two took on the role of main projector. Projector one was then turned off. The next reel would then be readied on projector one and the process repeated in around 15 minutes.
The New Vic received it's films on a Monday before screening. This gave the projection staff time to go through the films, check and clean them. If a film had been anyway damaged in transit there was a risk in those early days of a film sticking and catching fire. Being that original film stock was nitrate based this was a projectionists worse nightmare. Once cleaned and checked the film was stored in a fire proof cabinet. Each individual reel had its own cabinet; such was the fire risk. After the screening the film was transfered to the rewinding room, where you've quessed it film was readied for the next screening or it's transfer back to the distributers.
The projection room also had control of all other facilities. Such as lifting the curtain. Adjusting screen size. Controling lights and sound and music.
I've never seen a mis-load in the cinema; but I have seen it happen late night on BBC2. They were showing a Marx Brothers film and about half way through a reel was re loaded and that meant the whole film ran for about an extra half hour until they sorted it out. As for the exact story you'd have to ask the BBC.
In 1982 the Odeon was converted in to a triple. The original art deco style was not changed. Minor alterations were made. A new projector system was installed in cinema one, as described above. This flat bed system allowed the three screens to be run with only two projection staff. "Which was quite lavish." I've been to new multi plex cinemas where one projectionist runs all twelve screens. But that also means that you find that the film starts out of focus and you need to get a member of staff to sort it. The same can happen during the film as changes in the films emulsion can change it's focal characteristics.
Cinema one was the circle and the orginal screen was used. Screen two and three were in the section that was orginally the stalls. The projection offices being built into the orginal box seat sections. The cost of the screens and projection systems for two and three were around £14,000. Both systems were ItalianCinemaccincia, 35mm projectors with full auto rewind. Odeon 2's seating capacity was 293. Odeon 3's was 201.