20
Concepts in Photography
Depth of field
Portraits or still-life photos mostly acclaimed by people are the ones on
which the background is out of focus so the subject looks pronounced.
Depending on the focused areas, a photo can be blurred or sharpened.
This is called ‘a low DOF’ or ‘a high DOF’.
The depth of field is the focused area around the subject. Therefore,
a small DOF signifies that the focused area is narrow and a large DOF
means the focused area is wide.
A photo with a small DOF, which stresses the subject and makes the
rest of it blurred, can be obtained by using a telescope lens or selecting
a low aperture value. Conversely, a photo with a large DOF which
shows all the elements on the photo sharply focused can be achieved
by using a wide angle lens or selecting a high aperture value.
Small Depth of Field Large Depth of Field
What controls out-of-focus effects?
DOF depends on aperture value
The wider the aperture is (namely the lower the aperture value), the
lower the DOF becomes. Under the condition where the other values
including shutter speed and ISO sensitivity are equal, a low aperture
value leads to a photo with a low DOF.
20 mm F5.7 50 mm F22