Neo, the lead character of "The Matrix," may know martial arts, but the man who played him, Keanu Reeves, knows digital filmmaking.

As a producer of and narrator for the upcoming documentary "Side By Side," Reeves spent the past two years, between acting jobs, interviewing A-list directors and cinematographers about the evolution of digital cinema. The film traces Hollywood's shift from using photochemical film to digital prints and uses Reeves' interviews with the likes of George Lucas, James Cameron,...