In order to meet the strict requirements of filming at a National Historic Site, the production could not use the state box on the right side of the stage – where President Lincoln was actually shot – as it contained authentic relics from the assassination. Fortunately, the opposite side of the stage was identical. To solve this problem, Courtney and D.P. Ben Brunkhardt chose to film into a mirror. Together, large format camera company iWERKS and Camera Asst. Fred Wiegel engineered a front-surfaced mirror and mounting rig that stabilizes a reversed image. In order to ensure the film's authenticity, this meant everything from Booth's shooting hand to Lincoln 's mole needed to be reversed.