I’ve been using a method for testing shutter speeds is with a dSLR. This method only really works with really big shutters like the focal plane units in Graflex cameras. Extend the bellows (flip up the mirror if it’s an RB), take off the lens and any film back. stick your dslr on a tripod with its lens inside the bellows in the place of the lens board.
Point this assembly at something, turn off the lights and light that something and focus on it through the dSLR. Adjust your aperture on the dSLR to reflect the shutter speed that you are trying to test, and take a test shot with that speed on the dSLR. Then turn the dSLR’s shutter to 1″ and wind the Graflex’s shutter to that speed. Open shutter, fire Graflex’s shutter. Then compare.
I’ve found this method to be much easier than measuring an impulse and trying to compare microseconds to specific fractions of a second. On the dSLR you can look at a histogram approximate a percentage diffence in exposure. 10-20% is acceptable with black and white film.
