Hey, I recently bought a GAF XL-125 super8 camera at the local goodwill. It seems to be in great shape, and it runs like a champ. I have yet to expose any film with it though. I am nervous because there doesn't seem to be any exposure control with the camera, there is no iris control or anything of that nature. There is also this weird button on top that is flush with the body that when depressed moves this little clear filter inside the camera. I am just really confused, and I am wondering if my 5 dollar purchase can be used?