A Gaffer, or more formally, the Chief Lighting Technician, is in charge of the crew that runs the lighting on a film set. Gaffer Steve Mathis has worked on films including "Halloween," "Back to the Future," "Mrs. Doubtfire," "Moulin Rouge!," "Dawn of the Planet of the Apes," "Thor: Ragnarok," and more recently, "Wonder Woman 1984." In this episode, Steve talks about his responsibilities during pre-production and production.