Pentax K-5 Operating Manual page 129

Youcanfocus withthefollowing methods.
The camera automatically focuses on the subject when the
AF Autofocus
shutter release button is pressed halfway.
iF Manual focus Manually adjust the focus.
You can also choose the autofocus mode from AES (Single mode) where
the shutter release button is pressed halfway to focus on the subject and
the focus is locked at that position, and AF.O (Continuous mode) where
the subject is kept in focus by continuous adjustment while the shutter
release button is pressed halfway. The factory default setting is AES.
4
/ Turn the focus mode lever to AF.S
or C.