Sometimes you go to the beach or the park and late afternoon you might see a person walking around with a stick attached to a plate. This is a metal detector. You might recognize it from movies where soldiers used it to find mines and clear the road for troops and vehicles.
Filmmaking has been revolutionized by computerization and modern techniques. In the beginning the director relied on a cinematographer to capture the scene and then waiting around for the film to be processed and see the result. Then if not correct they had to reshoot the scene and wait around again. This took a very long time and lots of money for the actors and production people to make movies.