For what it's worth, I've been using Packard shutters for 62 years I prefer the instantaneous type. They are easy to spot as the shutter frame has a hole on one side, and a small diameter extension on the back side. These three leaf shutters are drivin by air from a bulb and hose that goes through the lensboard to the shutter cylinder. They come in different sizes for different diameter lenses. The larger shutters inst. speed is about 1/15 second. They are very simple to mount. If the lens sticks out in back of the lensboard, make a 1/2 inch box to mount the lens in front of the lensboard, with the Packard in back of the lensboard. I use them because they don't shake the camera. Packard shutters are still being made.