In the decades that both preceded and followed this anecdotal convergence of projection and physiology, experimental discoveries about human physiology were made by, among others, James Clerk Maxwell and Hermann von Helmholtz which comprehensively undermined the conception of human sight as objective and transparent, insisting – and indeed proving – its complexity, subjectivity, and its flaws. In these posts I will discuss the technical correspondence between the operation of DLP and human visual perception, with a particular emphasis on how contemporary projection has instrumentalised the knowledge of nineteenth century psychophysics, showing how the technical specifications of DLP projection are derived from a history of the empiricial measurement and quantification of subjective phenomena. This relationship is emblematic of what Jonathan Crary has described as “the reconfiguration of optical experience into synthetic and machinic operations that occur external to the observing subject” (p.226). The literal externalisation of the still beating heart in Czermak’s projections precedes a less violent externalisation of sight in the technics of contemporary projection. However, whereas in Czermak’s Spectatorium the frog heart projections served to demonstrate anatomical function through direct visual reproduction, in the case of DLP, knowledge of human physiology is used to ensure that its operation remains imperceptible to its audience. So, while for Czermak, projection was a transparent tool of instruction, the spectacle of DLP projection relies on the opacity of its technics to maintain the spectacle of its moving image. The psychophysical discoveries of Maxwell and Helmoltz are inscribed in DLP as a series of chromatic principles and temporal intervals within which certain operations must be occur to retain the illusory nature of its image. Whereas in the nineteenth century projection served to reveal physiological operations, projection now uses nineteenth century knowledge to conceal its operation.