I recently inherited a lovely Rochester Optical Co. Elite 5x8 with a Prosch Duplex. I've tried to check the shutter times using a couple of different methods: the "Arduino shutter speed tester (http://arduino.cc/forum/index.php/topic,8110.0.html) and a sound card method using the IR emitter and collector from the arduino technique. Both are indicating that the shutter at each speed opens twice, or has a bounce. The total time that it is open on it fastest setting is about 1/30th of a second. The diagram in audacity shows two approxamitely equal peaks.

Has anyone experienced bounce with these shutters? Or am I maybe using it wrong?

Thanks you looking.