Concepts in Photography
173
Aperture value and the depth of field
You can blur or sharpen the background of a photo by controlling the aperture. It is closely
related to the depth of field (DOF), which can be expressed as small or large.
A photo with a large DOF A photo with a small DOF
The aperture housing contains several blades. These blades move together and control the
amount of light passing through the centre of the aperture. The number of blades also affects
the shape of light when shooting night scenes. If an aperture has an even number of blades,
light divides into an equal number of sections. If the number of blades is odd, the number of
sections is double the number of blades.
For example, an aperture with 8 blades divides light into 8 sections and an aperture with 7
blades into 14 sections.
7 blades 8 blades