All the aligned combinations of shutter speed and f-stop are
equivalent exposures. The range of settings commonly used for
different types of subjects or imaging effects.
Nature photos are usually taken at f2.8-f4 to minimise depth
of field and to give the fastest possible shutter speed.
Portraits are usually taken at f5.6-f8. When you fill the
frame with head and shoulders, f5.6 gives enough depth of field
for the nose and hairline to be in focus only if you focus on
the eyes.
Landscapes are stationary so in some ways you don't have to
worry about shutter speed. You usually want the maximum depth
of field so you stop the lens down and using a tripod have a
longer exposure time. When water is flowing, the resulting slow
shutter speed is going to show current patterns on the water
eg 1/8 @ f 32.
Click here
to see some examples of different f/stops and shutter speeds.
