There
is an entire science behind understanding film performance,
of which latitude is only one. The aspect of latitude
that affects you most directly is the exposure lattitude
(plus or minus number of F/stops that can still achieve
a decently exposed image). This means "F/stop margin
of error" for most of us. It works like this, if
the film you're using has 1 stop exposure latitude and
your light meter tells you to set the F/stop to F-2.8
but your lens only goes down to F-4.5 - you can still
shoot at F-4.5 (if you can't change shutter speed) and
still get an acceptable image on film that can be doctored
by the lab. This is a handy piece of information when
shooting in low light conditions.
