>well, ISO + TIME + APERTURE are ingredients of EXPOSURE, and that should be all you need to know to start shooting. you know this and you can grab the newest high-end dslr or your grandpa's 35mm oldie and know what you're doing. the rest is just geekery.

Perhaps I misunderstood your point but that doesn't sound right. Iso does not control exposure: in case of film it is the sensitivity of a particular stock, and in case of sensors it's basically analog gain. Since to use a different ISO in a film camera you'd need to use a different roll or sheet of film, you can't vary ISO on a "grandpa's camera" very easily unlike with a digital camera.