In the Image Processing panel, crop the actor face from the image so as to
remove a needless background and enlarge the facial image you wish to work with.
Click the Zoom In
button (+ or Shift + "=") to zoom in the face area.
Click the Crop Tool
button and drag a marquee around the head to create a crop box,
as the actor animation is based on the head only.
If the actor head is slightly tilted,
use the corner handles
of the marquee to rotate the crop box
until the arrow handle is parallel to the nose.