MARCO ROMANO AT CASOLE ANSWERS TO CRITICS of the Serota film
Apr 052010

Currently there are two theories as to how Brunelleschi arrived at his rules of perspective, which deserve consideration but with which I cannot agree. David Hockney has demonstrated that Brunelleschi could have used a lens to throw the image of the Baptistery onto a surface on which it could then be traced. I could accept this theory if it were not for the evidence of Manetti, a friend of Brunelleschi’s, who had “held the painting (of the Baptistery) in his hands and seen it many times”. I have a second objection to Prof. Martin Kemps preferred theory (he actually lists six possibilities, Hockney’s was published after his book and was therefore not included). The second is that Kemp does not seem to take into account that there were many versions of perspective available at the time; and Brunellschi had to make a second demonstration to persuade people that his was the best.

Giotto and the ancients had a pragmatic means of conveying the space in a building or furniture based on it’s appearance. Ambrogio Lorenzetti and Simone Martini refined this perspective around 1330 so that their complete picture space was logical, and Kemp suggests that this perspective was used by Brunelleschi’s friend, Donatello as late as 1417 in his St. George relief, that is after Brunelleschi had made his first demonstration with the Baptistery. The new perspective did not reach Siena till the 1450s! Clearly the first demonstration was too complicated to follow, or perhaps it smacked too much of wizardry, with its use of two mirrors.

The solution that Kemp least favours I proposed in a lecture at the Slade c1978. (I do not suppose that I was the first to propose it) that is that Brunelleschi’s first demonstration was painted on a “a burnished silver” mirror. Manetti’s description says that “Filippo put burnished silver in the sky” but the reason he gives for this strange behaviour “so that the clouds would be seen to be moved by the winds that blow” seems scarcely credible for a man of Brunelleschi’s scientific bent. It diverts attention from the point he is making. I suggest that the Baptistery and surrounds were painted over the silver but Brunelleschi left the sky unpainted to explain his method.

Brunelleschi had to start from an image of reality that no one could question. The mirror image was such an image. The use of silver as the mirror is easily explained: Brunelleschi was a goldsmith, polished silver was the best reflector available and it had the further advantage over glass that one could scribe on its surface very precisely. The reflective surface could be touched without the thickness of glass intervening. Kemps main objection to this “simple” solution is that ones own image would blot out most of the Baptistery but this is not so. Once one has fixed the eye-point and the mirror one is free to move, to use either eye, and to look through the eye-piece with one’s head at what ever angle is convenient. By this method the size of the blot is no bigger than 2 cm in diameter, that is the distance between the pupil of the eye and the outer skull as reflected. This would not have been the slightest impediment as it need not blot out the outer corners of the Baptistery which are necessary points to fix the image. We can be certain that Brunelleschi would not have gone further with the work before analysing the geometry. The paint would have only been applied to clarify the image for others to appreciate how very like it was to the original. Naturally it needed to be turned round the right way this is why the peep-hole and second mirror were introduced. This method is not only the simplest as Kemp admits, it fits Manetti’s description in all but the one particular. Neither Kemp nor Manetti seem to have understood the need for the second mirror in righting the reversed image traced on the silver mirror.

Kemp’s further objections were:-

  1. that Manetti could not have been mistaken in thinking that the silver was applied to the sky area only. But clearly if the rest had been painted over why should he not have made this mistake. On the one occasion on which he held it in his hand we may presume he was preoccupied with seeing the image in the second mirror.

  2. Kemp goes on – it does not justify Manetti’s claim for Brunelleschi’s geometry. But it does of course require analytical geometry to arrive at the rules of perspective from the scribed image.

  3. The second of Brunelleschi’s demonstrations did not require mirrors; adds Kemp. No, that was why it’s straightforwardness finally convinced the doubters. It was presumably arrived at through the perspective geometry derived from the first demonstration.

(see “A Documentary History of Art vol.I.p171-2 . Anchor books 1957 for Manetti’s whole text in English)

One Response to “BRUNELLESCHI’S PERSPECTIVE”

  1. ANNE SHINGLETON says:

    Very interesting Nigel, thankyou.
    I must say that when I read Kemp’s description of how he thought Brunelleschi went about his drawing I felt I couldn’t follow it.
    The “silver sky” is a dead giveaway, and everything you say makes perfect practical sense.

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