Contributed by: c@tz
Usually, to access these
functions, depress the exposure release button halfway.
Aim the focus point at an object the same distance as
the subject of your exposure. Now hold the shutter
release button until you want to take the picture. This
will keep the camera focussed at that distance. Why
would you want to do this? Suppose you are taking a
picture of a moving object (such as a child at a soccer
game). You can't focus on your subject because your
subject isn't where you want them to be. So you
pre-focus on the spot where you will take the picture.
You don't have to wait for the camera to focus or wonder
if it focused, because it's already done.
The same action
controls the exposure lock. In fact exposure-lock and
pre-focus are in effect at the same time. Examples of
situations where exposure-lock might be useful are:
backlighting, contrasty light, and snowy scenes. The
light meter in your P&S (and all other cameras)
wants to make everything look medium grey. It will make
snow grey and black rocks grey. Sometimes you don't want
things to be grey. These are instances when you would
use the exposure-lock feature. In order to use the
exposure-lock feature aim the focus point at a medium
grey object or scene. Green leaves look grey to the
camera's meter. Asphalt pavement is close to medium grey
as is some tree bark. Try to see things in black and
white and average out the values in your head. Once
you've found a suitable subject, at the correct distance
(because the pre-focus will be triggered at the same
time), depress the shutter release halfway, point the
camera at your actual subject, and release the shutter.