Not so much shutters as about diaphragms this. The diaphragm actually could be placed anywhere and not just the center of the lens. Every part of a lens is a "lenslet" and contributes its own image and light rays to the whole. In a way, a lens is made up of an infinite number of tiny lenses. A larger diameter lens, let's say one of twice the area of a smaller one, has simply twice as many "lenslets". But how could that be since the first one already had an infinite number ... OK maybe that is an exaggeration because one can't have 2x infinity, right? ;) my brain hurts! andy
