17Concepts in PhotographyAperture value and the depth of fieldYou can blur or sharpen the background of a photo by controlling theaperture. It is closely related to the depth of field (DOF), which can beexpressed as small or large.A photo with a large DOF A photo with a small DOFThe aperture housing contains several blades. These blades move together andcontrol the amount of light passing through the center of the aperture. Thenumber of blades also affects the shape of light when shooting night scenes. Ifan aperture has an even number of blades, light divides into an equal numberof sections. If the number of blades is odd, the number of sections is double thenumber of blades.For example, an aperture with 8 blades divides light into 8 sections and anaperture with 7 blades into 14 sections.7 blades 8 blades
