Angle of view.
To determine the angle of view, draw a line AB equal to the focal length
of the lens. Construct BC perpendicular to AB and locate point C so that BC is
equal to one-half of the diagonal of the negative, (fig 2-16).
size of the angle by two to determine the angle of view.
Determining angle of view.
While angle of field is an unalterable optical characteristic of a lens,
angle of view is a variable depending on focal length of the lens, film size of
the camera with which the lens is used, and subject distance.
(1) With a normal lens, the focal length is equal to the diagonal of the
negative size used. When a normal focal length is used with a negative having