User blog comment:Pauolo/All pre-release info on Dishonored 2/@comment-1500935-20160530180224/@comment-1500935-20160531111316

Harvey Smith just confirmed it was made by the time of Dis 2, and added this about the device in Dunwall Tower: "recent to d2... that refraction lens device was a crazy Sokolov protoype that produced no lasting image"

So basically they invented the equivalent of a film, which was required to save images.