When people clap at the end of an industry screening, it usually indicates (a) politeness and (b) support of filmmakers whom some in the audience would like to meet and perhaps even work with some day. When people clap at a regular ticket-buyer screening, it means the film is a hit — period. They clapped at the end of Platoon, The Silence of the Lambs, Goodfellas, Titanic, The Wolf of Wall Street, etc.
What goes through my mind when this happens? I say to myself “this is what I love about seeing a film in a theatre…I love this kind of clear and immediate sense of how a film has played with a cross-section…you obviously can’t get this at home….I also love it when people laugh at a film by hooting and talking back to the screen, like when I saw Irwin Allen‘s The Swarm at the Quad back in ’78.”