For me the answer is the original Star Wars. After seeing it in the theater and coming home and looking at some of the souvenir magazines I immediately saw that the pics had missing picture information than what I remembered seeing in the theater. I was around 10 years old at the time and even then I saw the difference. Of course I know that a mag is different than the TV version, but when you see a pic that is nearly the same aspect ratio of a TV screen and compare it against a widescreen theater screen you can notice the difference. And of course seeing the film years later on TV in the pan and scan version, I already knew that something was missing. What was the first film that changed your mind about OAR and pan and scan?