HP R717 - Manual (Page 41)

41 Taking Pictures and Recording Video Clips
Using Focus Lock
Focus Lock allows you to focus on a subject that is not in the
center of the picture, or to capture action shots more quickly
by pre-focusing in the area where the action will occur. You
can also use Focus Lock to help achieve focus in low light or
low contrast situations.
1. Frame the subject for your
picture, or a higher contrast or
brighter object, within the focus
brackets.
2. Press the Shutter button halfway
down to lock the focus and
exposure.
3. Continue to hold the Shutter
button halfway down while you
re-frame or adjust your subject
for proper positioning.
4. Press the Shutter button all the
way down to take the picture.