Quote Originally Posted by Lee L
The sound card tester will work for focal plane shutters and with faster speeds......
In any case the sound card shutter tester will be good for any speed at which the curtain spacing is equal to or larger than the diameter of the phototransistor sensor.
Said another way: The phototransistor sensor would need to have a sensing diameter (field of view) equal to or smaller than the narrowest slit width. It is my impression that the generally available sensors have a fairly wide diameter (angle of acceptance). If my assumption is correct then the described method will not work