Yesterday member Drew Bedo sent me a PM asking if the circuitry in my Ghostmaster device might be of use in making a shutter speed checker. I wrote back that I did not think so, but at 4AM I awoke with the following idea.

This strategy is limited to x-synch leaf shutters. I am sure I could write up a patent application for this in few hours and be successful, but my previous experience with patents is they offer little advantage in a niche market. Once we start discussing it here, the invention is "open source" and cannot be patented.

The blades in a correctly functioning leaf shutter take only a few milliseconds to open or close(If not it needs a CLA). The electronic flash contact contact points close when the blades have flown fully open and open when they start to close. Therefore, the time of contact closure is very close to the exposure time. There should be some very useful information about the actual shutter speed Vs. that indicated if we connect an appropriate circuit to the electronic flash contacts. I know that this could be easily measured with an oscilloscope.

The scope will also show that the contacts bounce open again for a few micro seconds after closing when the shutter opens. Any circuit for measuring contact dwell time must be able to deal with this. Accurate measurements at very high speeds 1/250-1/500 may not be possible.
However, at the speeds at which most LF photographers work, less than 1/125, this approach could be very useful.

One advantage is that the measurement could be easily made with the lens in place on the camera, just before or even during actual film exposure. Perhaps the device could be incorporated in a cable release which also had an X-Synch connection.

Drew mentioned a possible smart phone interface. This could be wireless I suppose.

Any interest?