The smaller the hole, the more diffraction will ruin the already not so great image quality.
But you need a small hole to limit the 'angle of view', creating a sharper image. The smaller the hole, the smaller the area outside that is visible through it, the smaller the blur on each point on the film behind it. But get it too small, and the blur caused by diffraction will hit in big time, and it gets more blurry again. Just as when you make the hole too big.
Last edited by Q.G.; 01-12-2011 at 05:12 PM. Click to view previous post history.