Answer to Question 1
filtration
Rationale: Beam restriction is the single most important factor to minimize patient dose. Manual collimation, PBL, extension cones, and aperture diaphragms are all means to restrict the primary beam.
Answer to Question 2
calcaneus and subtalar joint
Rationale: The plantodorsal axial should demonstrate the entire calcaneus well with even density, but also show penetration of the subtalar or talocalcaneal joint.