Lately, I've picked up a few toy cameras from local thrift stores. These aren't Holga's or Diana's or anything with good documentation, but older cameras that a.) even if they had documentation, probably didn't publish anything as technical as shutter speed, and b.) even if the shutter speed was known, I'm not sure I'd trust it. Some of these cameras are twenty years old or more and parts wear. And, of course, these weren't manufactured for any sort of precision. So the really simple question is: Is there some slick way to calculate the shutter speed of a (film) camera? (It might seem counter to lomo thinking to even care; it's as much out of curiousity, as anything. But I do some street shooting where the camera is in motion, and knowing which of these cameras has the fastest shutter would be useful.) Thanks!