Pentax K-5 Operating Manual page 137

Locking ihe Focus (Focus
If the subject is outside the range of the focusing area, the camera cannot
automatically focus on the subject. In this case, focus the camera on the
subject in the focusing area, lock the focus at that position (Focus Lock),
and then recompose your picture.
1 Set the focus mode lever to AF.S.
2 Frame the desired composition
for your picture in the viewfinder.
3
4
Example) The person is out of
focus and the background
is focused instead.
Center the subject to focus in the
viewfinder and press the shutter
release button halfway.
The focus indicator II appears and you
will hear a beep when the subject comes
into focus. (When blinking, the subject is
not in focus.)
Lock the focus.
Keep the shutter release button pressed halfway. The focus will remain
locked.