Step 5.  Finding the optical center
for longer focal length lenses.

 
To find the optical center of a lens with a focal length of over 70mm you will probably need to set up you camera outdoors.
 

The picture above show how I have set my camera to align a pole and the edge of a window in the left of my frame.  The pole is about 5 feet from my camera and the window is about 30 feet from the camera.  The focal length of my lens is 100mm.

The picture above shows what my initial alignment looks like when I then pan to put the pole in the right side of the frame.  I will follow the procedure until the pole and window frame remain perfectly aligned just as I did with the nail and line setup.
 

You will need to follow steps 1-5 for all your cameras and various lenses making note of all final alignment details.

 

Go to step 6.