82 A SHORT GUIDE TO PHOTOGRAPHY / USB-TRANSFER MODE
The lens aperture controls not only exposure, but also
depth of field; the area between the closest object in
focus and the furthest object in focus. The larger the
aperture value, the greater the depth of field and the
longer the shutter speed needed to make the exposure.
The smaller the aperture value, the shallower the depth of
field and the faster the shutter speed needed to make the
exposure. Usually landscape photographs use a large
depth of field (large aperture value) to keep the
foreground and background in focus, and portraits use a
shallow depth of field (small aperture value) to separate
the subject from the background.
Depth of field also changes with focal length. The shorter
the focal length, the greater the depth of field; the longer
the focal length, the shallower the depth of field. Wide-
angle lenses also create a strong perspective which gives
a sense of depth in the image. Telephoto lenses
compress the space between the subject and
background and create a weak perspective.
The shutter controls not only exposure, but also the ability
to stop motion. Fast shutter speeds are used in sport
photography to stop action. Slow shutter speeds can be
used to show the flow of motion such as water cascading
over a waterfall. The use of a tripod is recommended with
slow shutter speeds.
A SHORT GUIDE TO PHOTOGRAPHY
Ev stands for exposure value. A change of
one Ev adjusts the exposure by a factor of
two.
WHAT IS AN EV?
+2.0 Ev 4X as much light
+1.0 Ev
–1.0 Ev
–2.0 Ev
2X as much light
1/2 as much light
1/4 as much light
Calculated exposure
