17
Concepts in Photography
Aperture value and the depth of eld
You can blur or sharpen the background of a photo by controlling the
aperture. It is closely related to the depth of eld (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 center of the aperture. The
number of blades also aects 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