Canon EOS ELAN7NE-33V - Manual (Page 90)

Basic Photography Terms
90
Depth of field
This is the range where acceptable focus can be achieved in front of and
behind the point of focus. The smaller the aperture value (the higher the
f/number), the deeper the depth of field. And the larger the aperture
value (the lower the f/number), the shallower the depth of field.
The depth of field is affected as described below:
(1) A smaller aperture value (a higher f/number) increases the depth of
field.
For example, stopping down to f/8 obtains a deeper depth of field
than f/4.5.
(2) A lens with a shorter focal length increases the depth of field.
A wide-angle lens obtains a deeper depth of field than a telephoto
lens.
(3) A longer distance between the camera and subject increases the
depth of field.
(4) The depth of field behind the point of optimum focus (2) is longer than
the depth of field in front of the point of optimum focus (1).
1 2
Depth of field
Point of optimum focus
Aperture set to f/2. Aperture set to f/22.