From around 1900, lantern projectors were part and parcel of art history’s efforts to become an ordered, systematic discipline. What the microscope was for biologists, the projector was for art historians. This apparatus offered a new mode of looking and a new way of doing art history. Specifically, the dual-slide projection, popularized by the Swiss art historian Heinrich Wölfflin, made it possible to develop a formal analysis of works of art from different periods. Art historians acquainted a systematic descriptive system.

First of all, this chapter will unravel how the projector was a linchpin of methodological premises among Wölfflin’s admirers. The comparative analyses cherished by prolific architectural historians as Sigfried Giedion, Rudolf Wittkower and Colin Rowe, all rooted in the side-by-side images from Wölfflin’s double projector. Next to that, this chapter will pay attention to how the projector affected the discursive economy of those developing alternative views on architectural history. By following both lines, it will be revealed how the projector generated a space within which varied discourses could be elaborated and transmitted, launched and modified.