I used the aperture technique while using an 8x20 camera during a 1 1/2 hour shot of a cathedral interior. While I was taking the picture (at f45) a mass started. I opened the aperture to f9 (the largest available) for about 3 or 4 seconds. This gave a ghosted appearance of the people who would have otherwise never showed. This allowed a sense both of the ephemeral as well as te cathedral's greater permanence.