Quote Originally Posted by alexhill View Post
Saw this on one of the blogs I follow (hackaday.com) and thought it was pretty awesome. http://www.rusted.free.fr/speed%20tester.html
Seems like I've been asking a lot of questions lately, for which I thank you guys. OK, another one: I intend to fabricate the tester in the referenced link to test my old 5-speed Betax. Now my thinking or logic might be flawed here, but it seems to me on an iris shutter, the shutter is open for less time on the edges of the round opening than the center, right? The shutter takes time to open and close, nothwithstanding the time it stays open. The edges are the last to be un-covered, and the first to be re-covered, right?. So if I make my tester with the phototransistor just a couple inches away from the rear lens element, it seems like I'd get a false reading. Seems like the phototransistor would have to be at the film plane to get a true reading. Feel free to correct my logic. Thanks.