To mark a sphere, select the Sphere Target Marking mode 
,
which is on the Target Marking drop down selector on the ribbon toolbar’s
Create Tab. On the image of the sphere in the photo,
click near the center of the sphere, hold the mouse down and drag a region
tightly around the sphere target (much like the region drawn around a regular
2D circular target). On release of the mouse button, the sphere inside the box
will be detected and subpixel marked. The resulting point can then be
referenced like any other point marked in PhotoModeler.