"Toomanyputters" <com> wrote in message
It should be used any time that it does not get in the way. It is supposed
to prevent light reflections on the different elements of the lens from
ruining the picture. It also helps prevent damage to the front of the lens.
It is especially useful outdoors in bright sunlight.
Some lens hoods cast a shadow when flash is used, or you may see some
vignetting at the widest angles of the lens, but a few test shots will show
you whether that is a problem.