There are as many ways of casting nonprofessional actors as there are of casting professionals, and as many ways to direct films with the one as with the other. Nonprofessionals can be dramatically inspired newcomers (such as Lynn Carlin in “Faces” or Souleymane Demé in “Grigris”), exemplary documentary-style incarnations of themselves (such as the entire cast of “The Exiles” or “People on Sunday”), blank slates for radical de-theatricalization (as in nearly the entire œuvre of Robert Bresson). But there are particular creative tensions that arise out of casting nonpros alongside movie stars. What interests me most about the casting of nonprofessional actors in dramatic movies is their disruptive presence, the way that their relative lack of technique and inexperience taking direction and playing to the camera create textures of the sort that directors have sought to achieve since the early days of narrative movies. The acclaim of Chloé Zhao’s “Nomadland,” in which Frances McDormand performs with a remarkable group of nonprofessionals, whom the production encountered on location, spotlights both the power and the pitfalls of such pairings. A more successful precedent is Roberto Rossellini’s 1950 film “Stromboli,” starring Ingrid Bergman alongside residents of the titular island. Their onscreen relationships are the very mainspring of the drama.