Murray Thompson has directed my attention to a neat little film "Projection: 85 Years of the Projection Booth in Movies", available on Vimeo. It is an edited, 12 minute compilation of scenes in, or involving, projection booth from 40 films, featuring the near extinction art of cinema projection. It has a very long url but a search under the film title, or its creator (Joseph O. Holmes) should find it.
Geoff Lealand was an Assoc Prof in Screen and Media Studies at the University of Waikato from 1992 to 2017. Now retired (not a word he favours), he writes social history, maintains this site, its Facebook and Instagram pages, as well as going to the cinema at least twice weekly.