Brunelleschi Device: The Deceptive "Proof" of Linear Perspective

Figure 1 – Brunelleschi Device
The device holds an image of an atrium flipped left to right. The viewer stands on the opposite side looking through the peephole in the centre partly at the actual atrium and partly at a mirror image of the photograph of the atrium.

I knew something had gone terribly wrong when I looked at my first snapshot of the Prairie landscape that I loved. The vast surround of infinite space that I experienced had vanished and been replaced by an impoverished facsimile that had narrowed, shrunken, flattened and deadened the original that it was supposed to represent. I thought I was a bad photographer or that I needed a bigger camera. The problem was in part the reduction of experienced reality to a flat surface in accordance to the geometric logic of linear perspective (depending on the lens, cameras and camera obscuras so long as they have pinholes instead of lenses render the world in linear perspective). Years later, when I learned to stitch together successive shots along the horizon I was somewhat more satisfied – but these photographic panoramas were a radical departure from linear perspective.

 

Figure 2 – Upward Converging Parallel Lines
Source: Ware, William R, Modern Perspective (Boston: Ticknor, 1882), Figure 26. This is the first image of upwardly converging verticals in a perspective treatise. Ware has copied the image from a stereoscopic photograph, "The Spire Of Salisbury Cathedral, Seen From Below," by William Sedgfield.

Perspective is a way of representing the world neither as the world is in itself nor as we experience it. It represents things that we know to be the same size as radically different in size (note the desks in the displayed photograph in Figure 1). It represents lines that we know to be parallel as converging to a point in the infinite distance, just as the horizontal lines of the walls and floor of the atrium in Figure 1 do. Look closely and you will see that at that point of convergence there is a circle; I have cut it open as a peephole for reasons I will explain shortly.

 

Perspective distortions in an image look perfectly natural to us now, but they must have shocked people when Brunelleschi first depicted them in the early 1400s. I am confident of this because we have written accounts of how incredulous people were in the early 1800s when artists proposed a particular perspective distortion that had been avoided until then – upward converging parallel lines (Figure 2).[1] The principle is the same as for converging horizontal lines, however, many learned experts were convinced that this was not how we see buildings when we look up at them and that it was preposterous to represent them that way.

 

Brunelleschi devised an ingenious proof for doubters of the "truth" of perspective. He built an apparatus that allowed people to compare a scene as we see it side-by-side with a perspective painting of that scene. The first step in his demonstration, and the one that I want to raise questions about, was to reduce "natural vision" to peering through a peephole. By this contrivance, viewers were deprived of binocular vision and, more importantly, the ability to move their head and eye as they surveyed the scene.

 

 

Figure 3 – Brunelleschi Device
Here the device is being tested in my front hall. The viewer looks through the peephole towards the scene. The mirror can be adjusted to match the scene with the reflected "painting" of the scene.

The peephole was drilled out at the centre of the painted panel and the viewer looked from the unpainted side of the panel towards a reflection of the painted side in a mirror held opposite it. In my reconstruction I fixed the panel and mirror to a tripod (figure 3). I allowed the mirror to be moved in a track closer to or further away from the painting (in this case a photograph of the scene). The idea here was to "focus" it relative to the scene. In the case of the atrium scene I selected one of the desks and viewed it through a split-screen: half reality and half mirrored-photo. By moving the mirror in or out I could get the two images to match with regard to size.

 

I also designed the mirror to slide side to side. As you slide the mirror (that depicts the perspective "painting") across the scene you can see that line-for-line, shape-for-shape the two are more-or-less identical. By this means perspective is proved! (Or so I put it to participants in a workshop in Lisbon.) When I demonstrated the device in Lisbon, even critically-trained scholars accepted the proof. However it has a fundamental flaw.

 

It compares perspective painting to a false standard of how we "really see." We rarely stop moving, and we experience the spatial world as much through our bodies as through our eyes. The images on our retina are a continually changing kaleidoscope of impressions from which our mind creates an impression of a stable external world – this stable reality is what we "see." Perspective painting shows us more-or-less what a fixed image on the retina looks like. But, as 18th-century philosophers were aware, we do not see images on the retina. We see through them to a world that our mind constructs for us from visual and tactile information and from conjecture and memory. If we always saw retinal images we would see the converging parallel lines and Brunelleschi would have had nothing to prove to people. But many, at his time and in the 19^th century (with regard to upwardly converging verticals) have adamantly denied that they saw any such thing.

 

The idea that we see paintings on the retina has confused people for centuries. The idea that perspective painting is the truth of how we see has also confused people. During the "perspective crisis" of the early 19^th century, conventional thinkers took painting as their guide and since painting represented horizontal parallel lines as converging to the horizon and vertical parallel lines as only ever parallel, this is how they thought that they saw the world.

 

The archaeology of the Brunelleschi device offers evidence for the following conclusions:

 

1) Perspective paintings (and photographs and retinal images) do not represent reality as we perceive it. (Yet for many it represents reality as they think they see it.)

 

2) There is a history of perception; in other words, the way we think we see the world changes culturally across time. Those changes are shaped by media of representation.