2) When converting viewing angles to obtain the focal length; do you measure the angle between between the extremities of the object and the front lens element or the angle between the object extremities and the sensor plane?
Neither. It is the angle at the nodal point of the lens.
|Leafless Tree. by SpartanWarrior|
|50 Shades On The Paris Metro by wam7|
from Your City - Commute
|Montana Badlands by stickpointed|
from The Tree
|Kestrel by Lance B|
from My Best Photo of the Week