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Perspective was allegedly discovered

Presumed depiction in Resurrection of the Son of Theophilus
(Artist: Masaccio)

Circa 1420, a landmark event (a sort of art performance of the day) took place in Florence at which the portrayal of perspective was allegedly discovered. Rather than discovery, it would be better to say that the artists of quattrocento began to use the technique of linear perspectival depiction. The most important attributes of perspective had been described and published prior to Brunelleschi by Euclid, Vitruvius, Ptolemy, Alhazen, Roger Bacon, John Pecham.

One sunny morning Filippo Brunelleschi appeared at the gate of the not yet completed cathedral, holding a little folder, and from this folder he took out a painting of the size of a 30- cm-sided square and a little mirror. Master Filippo was already considered a magician by half of Florence because of the dome being built without any scaffolding. No wonder a crowd had gathered for the demonstration.

Brunelleschi led people to the gate of the cathedral so that they should look into the direction of the Battistero outside the building. He gave the painting with a hole in the middle to somebody and asked him to keep the unpainted backside towards himself and to look carefully through the hole with one eye into the direction of the Baptizing Chapel. Then the master suddenly lifted the mirror in front of the painting, overshadowing the chapel from the viewer's sight, and asking loudly enough so that people further away could also hear: What can you see Sir? - Oh, the Battistero, Ser Filippo! And the audience was astounded. On the other side of the painting, the chapel was depicted perfectly and the hole was right on the horizon, just at the vanishing point. So the mirror showed just the same as reality it covered.

Florentine Baptistery and Palazzo Vecchio

We know the story in fullest detail from the memory of Antonio di Tuccio Manetti¹, but it is mentioned first (circa 1460) in the book by Antonio Averlino, also called Filatere², and also by Giorgio Vasari³. As the painting with the hole has not survived and there are unclear points in the anecdote, allow me to elaborate on the discovery in the following lines and with an experiment. The more I heard the story, the more obvious it became to me that something was missing from the recollections. Everybody reporting on the demonstrations explained in detail how the picture was supposed to be looked at, but nobody mentioned how you could make one. Yet this would have been the really interesting point.

If we reread Manetti's recollection, the most detailed one, we may notice that another mirror occurs in the story as well, as the painting with the hole itself was painted on a shining polished silver plate i.e., on a mirror. What could be the reason for this? From the point of view of the performance in front of the cathedral, the material of the painting had no relevance. The intriguing question arises: Why did Brunelleschi use a material so expensive at the time instead of the usual wooden panel? Manetti says that Brunelleschi did not paint the sky above the building, so that the clouds moving in the sky, or their reflection, would appear in the original on the painting. I can hardly believe that this explanation suffices. I can only imagine that these are the conclusions of a man who had come across the picture and tried to find a reason for having painted it just on a mirror. There must have been another reason for Brunelleschi to use a mirror. The only logical reason to paint a picture on a mirror is to have the subject already on the mirror as a reflection. The artist only draws around this reflection and covers it with paint in a similar way as the projected pictures would later be filled by some painter-successors in the case of camera obscura. For this, a fixed viewpoint was essential, and what could be better than a little hole?

Let us imagine the following arrangement: Filippo Brunelleschi is sitting behind the mirror with a hole turned to the Battistero at the gate of the cathedral. The mirror is placed on a small painter's tripod and nearly opposite to it another mirror and another tripod. The first mirror reflects the image of the octagonal form of the Baptistery onto the other mirror. Ser Filippo is looking at this reflected image from behind the first mirror, through its hole, and as the second mirror is placed in a position that he can reach it with his brush, he in fact paints the picture on the reflected image.

Installation: In memoriam
(Image: István Orosz)

It is not difficult to visualise this hypothetical method with the help of the diagrams above, and it is worth putting together the drawing machine consisting of two mirrors fixed on tripods. Of course, it is not that simple to use because of the one-eyed-technique. Filippo Brunelleschi is in fact a paraphrase of this drawing aid with mirrors, which may or may not have existed. We are supposed to look through a hole in the middle of the sheet from behind the back of the mirror fixed on a tripod towards the other mirror on the other tripod. An inscription can be read on this second mirror: BRUNELLESCHI. The second half of the name (LESCHI) is really there on the mirror, physically painted on the glass; but the first half of the name (BRUNEL), appearing in front of the painted text, is actually a reflected 14 image or rather the reflected image of a reflected image. Of course, this virtual part of the name also exists in reality. It is painted on a plate put on a third tripod and arranged in such a way that its image travels a path of exactly the right distance to the mirror with a hole and from there to the painted mirror so as to be reduced to the proper size. Following the anamorphic distortion and redistortion caused by the position of the tripods placed at an oblique angle to each other, the letters should also retain just the proper proportion.

There is a pencil sketch by Leonardo da Vinci that depicts a situation similar to the Brunelleschi demonstration4. As the sketch is very rough and indistinct, I cleared the image and I drew the diagram from another viewpoint, as well. The connection is more understandable if we recall Leonardo's famous notion: "The mirror is the master of the painter", and we interpret this notion not as a metaphor, but in the strict sense of the word. Mirror and reflection these words had a special meaning there at the Duomo. The large, uncovered building was the intellectual centre of Florence since the previous century and according to legend Boccaccio gave his famous Dante-lectures about the Divine Comedy in this church as well. He probably also explained the experiment by Beatrice with the three mirrors, as we can read in Paradise Canto II.

¹ Antonio di Tuccio Manetti: Vita di Filippo Brunelleschi, Milano, 1976.
² Antonio Averlino: Trattato di architettura, El Grassi ed., Milano, 1972.
³ Giorgio Vasari: A legkiválóbb festõk, szobrászok és építészek élete, Magyar Helikon, 1973.

For proposed reconstructions of Brunelleschi's demonstration, see Samuel Y. Edgerton, The Mirror, the Window & the Telescope; How Renaissance Linear Perspective Changed Our Vision of the Universe, Cornell University Press, Ithaca, NY, 2009, and István Orosz

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