If you include the foot on an AP ankle, you have followed the 1920 instructions instead of working out the best approach. you may as well direct the beam to the ankle and exclude the foot by centring above the ankle joint. A change of 5cm makes no detectable difference to the projection, but if you are a stickler to the traditional representation, centre on the ankle joint, then angle up until the collimation suits the ankle. Remember that changing the tube angle like This does not change the position of the tube focus, so the projection does not change. Tube angulation only changes collimation. kzbin.info/www/bejne/o4uzdZKdgdhoetksi=mBJqu0ngW2b0Bzlu