What are the two ways of linear incidence in foot orthosis photography?

Film: 8× 10 inch, vertical focal length: 75- 100 cm. Posture: The patient sits or lies on the photographic bed, with the knee joint of the examined side bent, the foot close to the surface of the cassette, the opposite leg straight to keep the body stable, and the third metatarsal base placed in the center of the cassette. Center line: vertically shoots into the center of the box through the bottom of the third metatarsal.