For the past couple of years, the issue of theatrical windows -- how long a movie is exclusively available in theaters -- has been the elephant in the room at CinemaCon. This year, the elephant is even larger than usual. Studios are eager to find a way to get movies in the homes of viewers sooner -- they figure many people would be willing to pay $30-$50 to watch a new movie in the comfort of their homes. But movie theater owners, the people attending CinemaCon, are desperate to hang on to that window of time that keeps movies in theaters only. Certain filmmakers are also devoted to giving their films a solid theatrical-only run, including Christopher Nolan, who was there presenting footage from his new movie Dunkirk.