A radiograph of an AP axial L5-S1 projection reveals that th…

A radiograph of an AP axial L5-S1 projection reveals that the joint space is not open. The following factors were used on this female patient: 80 kV, 40-inch (102-cm) SID, grid, 35° caudad angle, and CR centered to the ASIS. Which of the following factors needs to be modified to produce a more diagnostic image?