Most lenses are at its best when stopped down by about three stops from their maximum aperture; at this aperture most aberrations are at a minimum and diffraction has ont yet started to deteriorate the image.

• 大多数镜头的最佳光圈是从它大光圈调细约三。用最佳光，各种像差情况减到最少，衍射情况亦不至影响影像质素。