Pentax K-7 Operating Manual page 4

You can set the camera so that the focusing is performed when the AF
button is pressed.
I
Select [Enable AF] in [13. AF
Button Function] in the
[C Custom Setting 2] menu.
2 Cancel AF I
2
3
Auto focusing is performed by using the AF button or the
Enable AF
shutter release button. (default setting)
MF appears in the viewfinder while the AF button is
Cancel AF pressed. Autofocus does not activate when the shutter
release button is pressed. (Take your finger off the AF
button to return to normal autofocus mode.)
Press the
AF
button.
Auto focusing is performed.
When the subject is focused by pressing
AF.S (Single mode) the AF button, the focus lock is activated
while the button is pressed.
The subject is kept in focus when the AF
AEC (Continuous mode) button is pressed.
Press the shutter release button.
The picture is taken.