Pentax DS Operation Manual - Page 127

125 Fixing the Focus (Focus Lock) If the subject is outside of the range of the focus point area, the camera cannot automatically focus on the subject. In this situation, you can aim the focus point on the subject, use focus lock and recompose the picture. 1 Frame the desired composition for your picture in the viewfinder. You can use focus lock function when the subject you wish to focus on is not inside the focus point area. 2 Center the subject to focus in the viewfinder and press the shutter release button halfway. The focus indicator ] appears and you will hear a beep when the subject comes into focus. (If it is blinking, the subject is not in focus.) (Example) The person is out of focus 5 and the background is focused instead. Function Reference 3 Lock the focus. Keep the shutter release button pressed halfway. The focus will remain locked.