The Geometry of Vision: Hermann Maertens’ Optical Scale for a Deterministic Architecture

In 1870s the German architect Hermann Eduard Maertens grounded his Optical Scale research on Hermann Helmholtz and Franciscus Donders’ works about the physiology of vision and engrafted it in the tradition of Renaissance perspective and proportion theory’s applications to architecture and urban planning. This article describes the scientific core of his approach, in the context of a general revision of aesthetic enjoyment of artworks and a deterministic reorientation of human knowledge toward the industrial production; his elaboration of a triad of visual angles to determine size and organization of space according to visual targets; the diffusion of visual cones as a graphic tool to include perceptual values in the project; the immediate success of his formula among architects and urban planners but, at the same time, the critical reception of his static concept of urban perception; the means of transmission of his ideas in the XX century and their often unaware long-term influence on some postwar years researches.