Ernest, Welcome to the group, a lot of knowledge here. The F100 uses a geared system to advance the film and should be safe. It is not the little window that may cause the problems (black tape it to be safe), it is how the camera body counts sprockets in the film for advancing the film. Some bodies such as some Canons I think use infrared sensors to keep track of film advance. The F100 uses infrared, but not in the film mechanism. And, even if the body did use infrared to count sprocket holes in film, that is where the fogging would occur and therefore may still not be too serious of a problem. Take care, Gregory david Stempel FIREFRAMEi m a g i n g
