"For some odd reason we often take the term 'center of interest' a bit too literally
and we fell obliged to put the main subject square in the center of the viewfinder,
as if we were shooting it with a rifle instead of a lens.
Dead center in the frame though is probably the worst of all choices because
it surrounds your subject with equal amounts of space creating a stagnant
composition. Instead, shift your main point of interest to the left or right of center,
or slightly above or below the center of the frame to establish a more dynamic
use of space and a more natural feeling of balance.
One of the reasons we tend to center the main point of interest is that the
autofocus and light-metering indicators are in the center of the viewfinder
and so we center the subject to get sharp focus and good exposure. You can
do an end run around this, however, by pressing and holding your shutter-
release button halfway down to lock both focus and exposure.
You can then re-compose your image and still get a sharp, well-exposed picutre."