Also, as a follow up there are shutters for lenses in a barrel. They are called Packard shutters. They are usually mounted on the lens board behind the lens inside the bellows. They are controlled by a rubber hose and a bulb that you squeeze to make it work. You need to have a hole in the lens board for the tubing to sitck thru. After some practice you can generally control the action of the shutter and make it be about 1/30 to 1/60 of a second. This type of shutter is still made.