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Author Message   Winfried Rating: N/A Votes: 0 Posted on Sunday, January 18, 2004 - 02:38 am:    Rick, you are quite right. I just put a phototransistor behind the shutter, and of course this does not sense the whole 'stream of light' passing through the shutter. It would be more accurate to put the sensor in the film plane (focus point). According to international standards, shutter speeds are measured between the 50p.c. points of the rising and the falling edge of the light stream. Of course the 'fully open time' of a shutter set to 1/300 is quite shorter than the time measured to this standard. I found that most leaf shutters have rise and fall times around 1...2 milli-seconds which may cause a significant error when set to 1/300 where nominal open time is 3.3 milli-seconds.