Another important factor of
photographic expression is depth-of-field.
Depth-of-field is the range that
is sharp in the photograph when you focus on a given subject. When
the area of focus is wider, we say that the depth-of-field is deep
as opposed to the contrary when we say it is shallow. Adjusting the
aperture easily controls the depth-of-field.
Depth-of-field has the following
characteristics:
- With the aperture unchanged, the shorter the
focal length of the lens, the deeper the depth-of-field.
Telephoto lenses have relatively shallower depth-of-field. This
is one reason why wide-angle lenses are used for most snapshots
cameras.
- The smaller the aperture, the deeper the depth-of-field.
Therefore, if the lens' focal length remains unchanged, the depth-of-field
will be shallower at f:4 than at f:11
- With the aperture remaining constant, depth-of-field
becomes deeper the farther you are from the subject.
- Generally, at any given aperture, when one
point is focused, depth-of-field is shallower in the foreground
and deeper in the background, but it becomes relatively
shallower in both areas as the aperture is opened wider.
A shallow or increased depth-of-field
can help to create additional dimensions in the picture. For
instance, at a large aperture, it may be used to stress the subject
by blurring the surroundings. At a small aperture, you can get a
pretty sharp picture from the closest to the farthest distance.
|
