the necessity of anamorphism
In architectural discourse, perspectival drawings and photographs are constructed in the same ways and are nearly interchangeable. Perspective drawings and photographs utilize, almost exclusively, anamorphic perspective. Anamorphosis is defined as a "distorted projection or perspective requiring the viewer to use special devices or occupy a specific vantage point to reconstitute the image."ref While historically this process has been used to project images onto curvilinear objects (below) or correct the appearance of images that can only be viewed from certain angles (below), in architectural representation, anamorphic perspective is used to transform a space from a visual representation to a device of conceptual communication.
In Alberti's diagrams showing perspective projection, (above) rays from the represented scene strike a picture plane and are projected towards a viewer, establishing the viewers' position. The picture plane is perpendicular to and centered on the viewing axis, and assuming a standard cone of vision is sixty degrees and the axis of vision is horizontal, a minimally distorted perspectival drawing would show thirty degrees above the horizon, and thirty degrees below. For portraits this functions well, but for buildings, which are much taller than the observing subject, the upper limitation of a "balanced" perspective is clearly a problem. The solution, mechanically demonstrated by view cameras, is to slide the picture plane upwards, "selecting" a piece of an infinite picture plane to show to the viewer. This ability, called a shift, creates anamorphism because the picture plane is no longer parallel to the viewing angle.
At this point the laws of human vision and architectural representation diverge. When a human being looks up, the picture plane remains perpendicular to the viewing axis, and vertical lines of the structures a person sees begin to converge. In architectural representation, our attention is often drawn upwards (Image 2, left), but through anamorphosis all the vertical lines remain vertical. Experiential vision has two advantages over illustration: motion and spatial processing. When viewing a space or an environment our eyes have the opportunity to move, allowing our brain to assimilate a holistic representation of the visual input. Secondly, through our spatial processing capacity, we reconcile the fact that a building is vertical when we look at the ground floor, but seemingly falling backwards when we look up. As intelligent beings, we know a building is typical continuous and vertical, and instinctively resolve the visual contradiction. Without anamorphosis, spatial representation of built form might be something like the painting of Paul Cezanne, Turning Road at Montgeroult (right), having multiple breaks and ambiguities as spatial projections change with viewing angle. In the representation of space certain tradeoffs must be made, and traditionally faithful representation is disrupted and exchanged for an ordered view of the built environment and the communication of architectural ideas.