kunsthistorisches institut in florenz max-planck-institut
Studi e Ricerche 10 kunsthistorisches institut in florenz kunsthistorisches institut in florenz max-planck-institut max-planck-institut Direttori leonardo da vinci and optics Alessandro Nova e Gerhard Wolf Theory and pictorial practice
edited by Francesca Fiorani and Alessandro Nova
Marsilio This publication is kindly supported contents by the Lindner Center for Art History, McIntire Department of Art, University of Virginia
Editorial coordinator Francesca Fiorani
Editing Tracy Cosgriff Elizabeth Dwyer leonardo da vinci and optics theory and pictorial practice Plates Ricarda Fürnrohr Mandy Richter 9 Introduction Index of names Francesca Fiorani, Alessandro Nova Rodolfo Maffeis Linda Olenburg 29 Chiaroscuro, or the rhetoric of realism Mandy Richter David Summers
55 Technical images and painting technique In copertina in Leonardo’s portrait of Ginevra de’ Benci Leonardo da Vinci, Manuscript C, 1490 circa, Elizabeth Walmsley Paris, Bibliothèque de l’Institut de France (Manuscript 2174), fol. 19r 79 Leonardo’s prospettiva delle ombre. Another branch of non-linear perspective Graphic designer Janis Bell Tapiro, Venice 113 «Come calamita il ferro»: ©2013 by marsilio editori® s.p.a. in venice Leonardo da Vinci dalla magia alla prospettiva (1487-1492) Fabio Frosini First edition: November 2013 www.marsilio.it 155 Il fratello del nulla. isbn 978-88-317-1494-5 Il «punto» nell’ottica di Leonardo
Up to 15% of this book may be photocopied for personal Frank Fehrenbach use by readers provided they pay the siae the fee established by art. 68, clauses 4 and 5 of Law no. 633 of 22 April 1941. 185 Leonardo’s painting technique in the Virgin and Child with St. Anne Photocopies for professional, economic or commercial purposes or in any way different from personal use may be Cinzia Pasquali made, but only after obtaining specific authorization from the Centro Licenze e Autorizzazioni per le Riproduzioni Editoriali 195 Il primato dell’occhio e della pittura: (cleardi), Corso di Porta Romana 108, 20122 Milan e-mail [email protected] i ritratti milanesi di Leonardo e il Paragone delle arti and web site www.clearedi.org. Pietro C. Marani 217 Luce e ritratto nel Trattato della pittura di Lionardo Da Vinci leonardo da vinci and optics Romano Nanni Theory and pictorial practice 247 L’«underdrawing» dell’Annunciazione e la prospettiva di Leonardo Roberto Bellucci
265 Leonardo’s optics in the 1470s Francesca Fiorani
293 Leonardo, optics and ophthalmology Dominique Raynaud
315 The measure of sight, the measure of darkness. Leonardo da Vinci and the history of blurriness Frank Zöllner
333 L’Adorazione dei Magi di Leonardo da Vinci e le prime indagini diagnostiche presso l'Opificio delle Pietre Dure. Oltre il visibile Cecilia Frosinini
353 Index of names Linda Olenburg, Mandy Richter
356 Index of works and manuscripts Rodolfo Maffeis, Linda Olenburg
358 Credits roberto bellucci allineati) appare sproporzionata, non solo in relazione all’edificio ma anche francesca fiorani per il rapporto interno tra chioma e fusto, così come appaiono spropor- zionati sotto questo aspetto anche tutti gli altri alberi. Tutti elementi che leonardo’s optics in the 1470s potevano avere un senso ed una loro coerenza ottica e dimensionale se non relazionati gli uni agli altri, in una fase, cioè, in cui sono stati studiati sepa- ratamente e poi, attraverso un pensiero ancora parcellizzato, riportati sulla tavola a comporre una raffigurazione unica. Sembrerebbe essere la loro giu- stapposizione a renderli incoerenti l’uno con l’altro e quindi a richiedere da parte dell’artista una correzione sostanziale. Il momento di trasformazione dell’impianto prospettico originario, dun- que, parrebbe essere avvenuto al momento finale della realizzazione dell’im- pianto generale della scena e comunque prima dell’inserimento delle figure Leonardo’s early drawings and paintings display stunning optical ef- (che come già detto, erano però previste e il cui ingombro era forse somma- fects that far exceed traditional artistic practices north and south of the riamente definito). Per quanto potessero essere state studiate in precedenza, Alps, especially in their treatment of the atmosphere (fig. 1). Such exam- attraverso schizzi e disegni preparatori su carta, le figure poterono sembrare ples are generally explained in light of Leonardo’s preoccupation with the a Leonardo stesso per così dire «sproporzionate» nel momento in cui furono effects of the atmosphere on colors, details, outlines; likewise, it is typi- disegnate sulla tavola, in relazione allo spazio definito dall’architettura dell’edi- cally understood that contrasts of light and shadow in Leonardo’s early ficio. L’ipotesi che finora era stata invece presa in considerazione per spiegare works emerged from artistic practice and from his acute observation of queste modifiche e le apparenti incongruenze che ne derivano è stata quella nature. Further, it is usually believed that Leonardo sought an optical ex- di un adattamento da parte dell’artista alla collocazione originaria dell’opera, planation of the phenomena he had painted only later in his career, from forse in posizione fortemente scorciata e non fatta per una percezione fron- the mid 1480s onward. Indeed, few surviving writings from the 1470s tale, così che le modifiche fossero utili ad accentuarne la vista privilegiata26. suggest that he had any foundation in optics. And yet, if one keeps in L’ipotesi resta difficile da suffragare ulteriormente, data l’incertezza su questa mind the general rule that one sees what one knows, it is conceivable that destinazione originaria dell’opera. Nel riproporre, quindi, il dubbio se si sia behind Leonardo’s early works lies a greater awareness of optics than has trattato delle conseguenze di un errore o di un vero artificio, di un espediente been acknowledged. o di incongruenza, è particolarmente suggestivo concludere con una citazione The matter of Leonardo’s early knowledge of optics is not just a chrono- dagli scritti di Leonardo, in cui l’artista sembra quasi descrivere ad un allievo logical one, although chronology has its significance. It is also methodo- la possibilità che a lui stesso si è presentata nella elaborazione di questa com- logical and necessitates reconsideration of the nature of Leonardo’s writ- posizione: «Onde, avendo tu bene a mente i precetti delle mie regole, potrai ings, as well as of the influence of the Arab philosopher Ibn Al-Haytham, solamente col racconcio giudizio, giudicare e conoscere ogni sproporzionata known in the west as Alhazen (or Alhacen), whose writings have always opera, così in prospettiva, come in figure o altre cose»27. been regarded as fundamental to Leonardo’s art theory, but understood as less important to his painting of blurred edges and reflected colors.
26 Degl’Innocenti, 1978 (vedi n. 5), pp. 276-278; A. Natali, «Dubbi, difficoltà e disguidi nell’Annunciazione di Leonardo», in: L’Annunciazione di Leonardo (vedi n. 5), pp. 37-59. leonardo’s early writings 27 Leonardo da Vinci, Il Codice Atlantico della Biblioteca Ambrosiana di Milano, tra- scrizione diplomatica e critica di A. Marinoni, Firenze 1975-1980, f. 218v (cit. in E. Solmi, Leonardo da Vinci. Frammenti letterari e filosofici. Favole, allegorie, pensieri, paesi, figure, Among thousands of Leonardo’s surviving notes, only a few date from profezie, facezie, Firenze 1925, pp. 78-79). the 1470s—either Leonardo did not write much, or he discarded later what
264 265 francesca fiorani leonardo’s optics in the 1470s he had written then. Restricted to a handful of loose sheets and a few folios from the Codex Atlanticus, these early notes pertain mainly to water and lifting machines, and only a limited number of them deals with optical matters. Generally, these early and sparse optical writings are concerned with the concave and burning mirrors that were used to build the palla crowning the dome of Florence cathedral, a complex operation that Ver- rocchio masterminded between 1468 and 1471, when Leonardo was an ap- prentice in his workshop1. In one of these early sheets on concave mirrors (Codex Atlanticus, fol. 801r, datable 1478-1480), Leonardo added a note referring to «libri incat- enati» or chained books—the books that were chained to desks in public Florentine libraries, most notably in the library of San Marco. Given that this note appears among sketches of concave mirrors and that many opti- cal texts that we know Leonardo read later in life were actually kept in public libraries, it is possible that Leonardo is referring here to optical texts, but there is no way to be certain about it. More compelling evidence of Leonardo’s possible exposure to optics in the 1470s is suggested by another folio from the Codex Atlanticus, fol. 847r, dating from the same period and similarly related to the palla operation (fig. 2). This folio is well known to scholars, but detailed reexamination is worthwhile since the page contains a drawing by Leonardo that often goes unnoticed but which may suggest that Leonardo was familiar with De aspec- tibus, Alhazen’s monumental work that was at the origin of medieval optics.
leonardo’s first diagram of the eye
Folio 847r of the Codex Atlanticus is famous for a drawing in the up- per part of the sheet, where Leonardo sketched one of the machines Brunelleschi had invented to erect the dome of Florence cathedral (fig.
1 On Leonardo’s early drawings relating to Florence cathedral see: P. Galluzzi, Mechan- ical marvels. Invention in the age of Leonardo, Florence 1996, pp. 93-115; S. Dupré, «Optics, pictures and evidence: Leonardo’s drawings of mirrors and machinery», in: Early Science 1. Leonardo da Vinci, and Medicine, x, 2005, pp. 211-236; on the palla operation see D. Covi, «Verrocchio and Baptism of Christ, 1478 the palla of the Duomo», in: Art the ape of nature. Studies in honor of H. W. Janson, ed. by circa, Florence, Uffizi, M. Barasch, L. Freeman Sandler, New York 1981, pp. 151-169. detail of landscape
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2. Leonardo da 2). Leonardo labeled this machine «viticcio di lanterna», identifying it un- Vinci, Codex equivocally with the screw of the revolving crane that Brunelleschi had Atlanticus, 1478-1480 circa, invented to build the cathedral’s lantern. Leonardo knew Brunelleschi’s Milan, Venerabile revolving crane well, since it was used in 1471 to place the palla atop the Biblioteca dome, an event he may have witnessed as an apprentice in Verrocchio’s Ambrosiana, fol. 847r workshop and that he nostalgically recalled in his sixties in a note: «Re- member the solders that were used to solder the palla of Santa Reparata»2. The passage does not have the poetic flare of a childhood memory, but is nonetheless a recollection of what must have been a crucial formative experience in practical optics. It is Leonardo’s drawing on the lower part of folio 847r of the Codex Atlanticus, just below the viticcio di lanterna, that is especially useful for assessing Leonardo’s possible knowledge of theoretical optics. Here Leon- ardo drew a diagram of the eye, which, to my knowledge, is Leonardo’s first diagram of its kind. It is sketchy, basic and fragmentary, even by Leon- ardo’s standards, and the drawing has gone largely overlooked, perhaps because it does not achieve the sophistication of his later anatomical dia- grams. However, the diagram suggests that at the same time that Leonardo was mastering the optics of burning mirrorsfor the palla operation, he was also exposed to optics more broadly3. In this first diagram of the eye, Leonardo drew luminous rays that are emitted toward (or from) the eye and thus define the visual field. He represented the crystalline humor in the shape of a lentil, slightly curved. Leonardo may have derived this sketchy anatomical drawing of the eye from a variety of texts that we must imagine commonly circu- lated throughout artists’ workshops. But it is the note accompanying the diagram that points toward a direct knowledge of Alhazen’s De
2 Leonardo da Vinci, I manoscritti dell’Institut de France, ed. by A. Marinoni, 12 vols. (Manoscritti A-M), Firenze 1986-1990 [hereafter Leonardo, Manuscript A-M], vol. 7: Ma- nuscript G, fol. 84v. 3 C. Pedretti, The Codex Atlanticus of Leonardo da Vinci. A catalogue of its restored sheets, New York 1978, vol. 2, p. 144, dated folio 847r to 1478-1480 based on Leonardo’s handwrit- ing. It should be mentioned, however, that the layout of words and images on this folio suggests that Leonardo did not sketch his diagram of the eye for the first time here, but rather that he reorganized on this sheet notes and drawings that he previously had done. Thus, as Pedretti correctly proposed, the folio is dated 1478-1480, but its content may date to an earlier period. Indeed, the top drawing refers to events of the early 1470s.
268 269 francesca fiorani leonardo’s optics in the 1470s aspectibus4. Here Leonardo wonders about possible causes that explain sarily as indications of his support for it, but should rather be regarded as the difference between an image received at the front of the crystalline notes taken from authoritative texts for his own future reference. humor and an image received at its back: Second, Leonardo compared the eye to a palla di vetro, reasoning that, like water, the palla di vetro of the crystalline humor makes objects appear perché l’occhio, venendo le cose sulla sua superficie piccole, gli paian grandi bigger. This sentence is peculiar; the question that follows is not whether nasce che la popilla è specchio cavo. E ancora osserva per esempio una palla di Leonardo was right or wrong, but from where he might have borrowed this vetro piena d’acqua, che qualunque cosa si mette dalla sua parte, o dentro o fuora, idea. Indeed, the comparison between the crystalline humor and a palla di 5 par maggiore . vetro is suggestively similar to Alhazen’s description of the crystalline humor as a white, small, humid sphere, which is essentially watery in nature. This note and diagram reveal several interesting elements. First of all, Leonardo’s notation that le cose come to the surface of the eye (superficie Leonardo writes that «the objects (le cose) come upon the eye», not the oth- dell’occhio) rather than to a point within it is most revealing. It seems that er way around. This sentence documents that, by the 1470s, Leonardo was here, as Leonardo ponders how small objects that reach the eye come to already fully aware of intromission theory, which Alhazen had introduced be perceived as large, he also affirms that it is the surface of the eye that to counter extromission theory and which Alhazen’s medieval Christian receives them, rather than a point within it. Martin Kemp and James Ack- followers (Bacon, Pecham and Witelo) accepted. Although Leonardo’s erman have shown that Leonardo accepted Alhazen’s theory of the surface knowledge of intromission theory should not be surprising, it contradicts of the eye from 1508 onward, when he wrote about it explicitly in Manu- the traditional understanding of Leonardo’s optics, which has generally script D, a notebook dedicated to the anatomy of the eye. Codex Atlanticus, held that Leonardo supported extromission theory first and came to ac- fol. 847r, however, shows that Leonardo was familiar with Alhazen’s theory 6 cept intromission only later in life . In light of the diagram of the eye in already in the 1470s, forcing us to revise our understanding of how Leon- Codex Atlanticus, fol. 847r, it is possible to ascertain that Leonardo knew ardo conceived of the formation of the image within the eye7. Moreover, intromission theory during his Florentine years. Further, it can now be the specific reference to the surface of the eye suggests a direct knowledge suggested that his notes on extromission should not be interpreted neces- of Alhazen’s De aspectibus, and begs the question of whether Leonardo un- derstood the role of the surface of the eye within Alhazen’s entire theory of knowledge, and, if so, whether this understanding influenced his painting of blurred edges and reflected colors. 4 On the influence of Alhazen on Leonardo, see S.Y. Edgerton,The Renaissance re- discovery of linear perspective, New York 1976; B.S. Eastwood, «Alhazen, Leonardo, and late medieval speculation on the inversion of images in the eye», in: Annals of Science, the surface of the eye xliii, 1986, pp. 413-446; M. Kemp, «The Hammer lecture (1992). The beholder’s eye: Leonardo and the ‘errors of sight’ in theory and practice» in: Achademia Leonardi Vinci, v, 1993, pp. 153-162; J. Bell, «Leonardo and Alhazen: The cloth on the mountain top», in: The relevance of the surface of the eye to vision was one of Alhazen’s Achademia Leonardi Vinci, vi, 1993, pp. 108-111; D. Raynaud, «La perspective aérienne de distinctive contributions to optics and represents a fundamental compo- Léonard de Vinci et ses origins dans l’optique d’Ibn Al-Haytham (De aspectibus, iii, 7)», in: Arabic Sciences and Philosophy, ixx, 2009, pp. 225-246; Id, in this volume, pp. 293-314. 5 Leonardo da Vinci, Il Codice Atlantico della Biblioteca Ambrosiana di Milano, ed. by A. Marinoni, Firenze 1975-1980 [hereafter Leonardo, Codice Atlantico], fol. 847r. 6 M. Kemp, «Leonardo and the visual pyramid», in: Journal of the Warburg and Cour- 7 Kemp, 1977 (as in n. 6); Ackerman, 1978 (as in n. 6). See also D. S. Strong, Leon- tauld Institutes, xl, 1977, pp. 128-49; see also J. Ackerman, «Leonardo’s eye», in: Journal of ardo on the eye. An English translation and critical commentary of Ms. D in the Bibliothèque the Warburg and Courtauld Institutes, xli, 1978, pp. 108-146; D. Summers, The judgment of nationale, Paris, with studies on Leonardo’s methodology and theories on optics, New York/ sense. Renaissance naturalism and the rise of aesthetics, Cambridge/New York 1987. London 1979.
270 271 francesca fiorani leonardo’s optics in the 1470s nent of his theory of knowledge. While Alhazen’s medieval Christian fol- on the sensory data it receives, especially if this data reaches the eye under lowers—Bacon, Pecham and Witelo—accepted his notion of the surface unfavorable conditions. For Alhazen, the conditions that affect vision are of the eye, they did not accept the full range of its consequences within distance, orientation, light source, body, opacity, transparency of the me- Alhazen’s greater theory of knowledge8. dium, time, and health of the eye, and he carefully lists the many situations In De aspectibus, Alhazen debated at length about the formation of the in which different conditions, interacting with one another, send contra- image on the surface of the eye, which he supplemented with elaborate geo- dictory sensory data to the faculty of the soul: «The only reason sight errs metrical demonstrations9. But instead of these highly theoretical discussions, in perceiving forms», Alhazen writes, «is because one or more of the afore- it was one simple experiment based on everyday experience that made the mentioned conditions has fallen outside of the range of moderation»10. surface of the eye easily comprehensible. If a needle is placed close to the Alhazen’s theory of vision was fully understood by Bacon, Pecham and eye, the needle does not cover the entire field of vision but only a part of it. Witelo, who transmitted to the Latin west his intromission theory and his According to Alhazen, this fact demonstrates that the visual pyramid (virtú mechanism of vision, as well as his use of geometrical optics as an abstract visiva) does not end in a single point within the eye, which the needle would model for investigating vision and his notion of visual rays as non-physical cover, but rather ends in a larger surface that the needle cannot obstruct. entities. The terminology of these medieval theorists, however, is often For Alhazen, the surface of the eye as the site of vision was a funda- different. For instance, Alhazen distinguishes forma from imago—forma mental step in distinguishing three different ways to acquire knowledge. is the quality of things, and imago a refracted image; one is real, the other The first isintuitio —that is, the vision of the centric ray, which never errs. virtual—while Bacon and Pecham speak of species. But forma and species The second is aspectus, or the vision of other rays, which gives momentary behave similarly since both emanate from an object in all directions as a knowledge of surrounding elements; the aspectus is not perfect, but it has power—not as a physical entity—that affects the eye qualitatively rather to be verified—or certified, to use Alhazen’s terminology—withintuitio . than quantitatively. But unlike Alhazen, Bacon and Pecham considered The third way to acquire knowledge is cognition, which is the elaboration the eye to emit its own species, which meet the species of external objects of the soul on the sensory data that come from intuitio and aspectus. Con- and facilitate vision. Although seemingly minor, this change determined sequently, the acquisition of knowledge is the result of a constant process a major difference in the role Bacon, Pecham and Witelo assigned to the of certification betweenintuitio and aspectus, between the center and the senses in the acquisition of knowledge. periphery, between an object and its surrounding elements. Mediated and Despite the fact that for Alhazen vision never errs and that mispercep- extended over time, cognition is always temporary and never immediate. tions occur only because the faculty of the intellect processes incorrect According to Alhazen’s theory of knowledge, vision never errs because sensory data that reaches it in unfavorable conditions, for Bacon and Pe- its mechanisms and the anatomy of the eye are perfect. If misperception cham the eye can err since, like any other object, it emits species. Unlike in occurs, it is due to erroneous elaborations made by the faculty of the soul Alhazen’s model, which considered the faculty of the intellect to operate only on the sensory data given by the eye, which is always correct, in their system the virtú visiva, the faculty of the intellect, intervenes in vision. Because of this different conception of the virtú visiva, Bacon, Pecham and 8 On Alhazen’s influence on medieval optical writers, see G. Federici Vescovini,Studi Witelo treat the nature of light as a metaphor for the nature of the divine, sulla prospettiva medievale, Torino 1965. On Alhazen’s theory of knowledge, see Summers which ultimately brings one closer to divine knowledge. By contrast, op- (as in n. 6); The optics of Ibn Al-Haytham: Books i-iii: On direct vision, ed. by A. I Sabra, tics for Alhazen is an end to knowledge of the world. London 1989; Alhacen’s theory of visual perception. A critical edition with English translation and commentary of the first three books of Alhacen’s De aspectibus, ed. by A.M. Smith, 2 vols., Philadelphia 2001 [hereafter Alhazen, De aspectibus]; H. Belting, Florence and Bagdad: Re- naissance art and Arab science, Cambridge/MA 2011 (German: Munich 2008), pp. 90-99. 9 Alhazen, De aspectibus, Book i, 15-16, as well as Book vii, 37. 10 Ibid., Book iii, 3.34; Book iii, 3.5, on the conditions of vision.
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It is Alhazen’s theory of knowledge, rather than that of his medieval Codex Atlanticus, fol. 676r-v followers, that is better reflected in Leonardo’s thinking. Although Leon- On the verso of Codex Atlanticus, fol. 676, Leonardo wrote a title sen- ardo read the work of Bacon, Pecham and Witelo later in his life, it is Al- tence that comments on the strength of similitudini entering the eye as hazen’s system that provides the theoretical framework for Leonardo’s art a sort of preface to the entire page: «Quelle similitudini si riserveranno theory, including the famous statement: «experience never errs; it is only piú nell’occhio che da piú luminoso corpo nate sono» (fig. 3). He then our judgment that errs»11. Furthermore, Alhazen’s notion of the surface of proceeded to draw two large diagrams, one in the middle of the page il- the eye provided the framework for Leonardo’s painting of blurred edges lustrating the surface of the eye and the other at the bottom explaining and reflected colors, which became distinct characteristics of his art from the creation of ombre e luci in relation to the distance and size of a spheri- the 1470s onward. cal object and a light source. Leonardo wrote an accompanying text for the lower diagram. The text starts above the figure and continues below it, so that the diagram is literally embraced by words. Then he added an blurred edges and the surface of the eye explanatory text below the other diagram—the one on the surface of the eye, which he had drawn in the middle of the page. But he miscalculated The clearest instances in which Leonardo explained the connection the length of the text, ran out of space, jotted a reference sign that looks between the surface of the eye and his art of blurred edges and reflected like a «4», and continued to write above the diagram in an area of the sheet colors come from two important folios that are now separated—one folio that he had originally reserved for something else, possibly an explanation is in the Codex Atlanticus, the other in Manuscript C—but they may have of the similitudini dell’occhio mentioned in page’s title. Here the diagram originally been united on Leonardo’s desk around 1490. In these years he is also engulfed in words, but the text above it is in fact the conclusion of assembled Manuscript A, which contains large optical sections, wrote the Leonardo’s argument. Read in the proper order, Leonardo’s intentions are Paragone and painted famous portraits. He also wrote important notes on clear. He plans to demonstrate «come la prospettiva, offizio dell’occhio, non these two sheets about various optical themes, including the surface of the si riduce in punto», and resorts to an experiment with a small object placed eye, the comparison between the sensory perception of the eye and the ear, near the eye, evidently modeled after Alhazen’s experiment with a needle: and the outline of a book on shadows. As Carlo Pedretti has noted, Codex Atlanticus, fol. 676r-v, and Manuscript C contain related topics and also Pruova come la prospettiva, offizio dell’occhio, non si reduce in punto. La share physical characteristics: they are written on the same kind of paper ragione è questa: se tu antiporrai vicino all’occhio una cosa assai minore che which is almost identical in size—Manuscript C measures 307 mm × 220 la papilla, tu vederai, dopo essa opposizione, ciascuna cosa come se essa fosse mm, and Codex Atlanticus, fol. 676r-v, 305 mm x 220 mm. Pedretti has antiposta cosa transparente fusse. Diciamo che essa papilla sia o p e che ‘l punto suggested that , fol. 676r-v, may have been originally part immaginato dai prospettivi sia n. Or non vedi tu che se tu li opponi la grossezza Codex Atlanticus 13 of Manuscript C, or, at the very least, that the sheet came from the same f, che ‘l loco b c sará da esso f occupato? Onde che la sperienza [...] . rim of folios that comprise Manuscript C 11. Since their relevance to Leon- ardo’s painting of blurred edges has never been pointed out, it is worth re-examining these folios. 13 Leonardo, Codice Atlantico, fol. 676v. The text continues: «Ogni cosa transparente infra a e, che non è un punto ma tutta la papilla, è equale nella virtù visiva, ma non equal di potenzia, perché quella parte ch’ é piú distante dal suo centro, men discerne le cose. Essendo la virtù visiva equalmente per la popilla infusa, nessuna cosa di minore quantità d’essa a essa propinquamente antiposta, potrà occupare alcuna parte del distante obbietto. La pruova farai così. Diciamo o p essere la
274 275 francesca fiorani leonardo’s optics in the 1470s
3a-b. Leonardo da Vinci, Codex Atlanticus, 1478-1480, Milan, Venerabile Biblioteca Ambrosiana, fol. 676r-v
276 277 francesca fiorani leonardo’s optics in the 1470s
The relation between the surface of the eye and the perception of ombre After the Proemio he wrote a quick definition of a shadow—«ombra è e luci is reinforced on the recto of the same folio, which can be dated to privazione di luce»—and then composed an elaborate description of his the same time as the verso on the grounds of their similar ductus and the book, which he divided into seven parts—a tantalizing number since it is title sentence, which is laid out similarly on both sides of the sheet (fig. 3). identical to the books of Alhazen’s De aspectibus15. Leonardo’s treatise ad- Here Leonardo compared different sensory experiences and asserted that dressed issues of increasing complexity pertaining to the qualitative and visual perception is quicker and more durable than auditory perception: quantitative treatment of light and shadow, which Alhazen had debated to «Tanto quanto l’occhio in suo offizio è più presto che l’orecchio, tanto più an extent unmatched by other medieval writers. The impetus for Leonar- reserva le similitudine delle cose in esso impresse». This type of compari- do’s intended book also seems to be rooted in Alhazen as for both without son between different sensorial perceptions was the basis for his Paragone, shadows we do not know objects, «what is placed inside them and their and is one of the few bits that has come to us from Leonardo’s original edges, especially if they do not end on a field colored differently from the manuscripts14. Although the sentence serves as an introduction to the en- tire page, it is followed by a large empty space that Leonardo intended to fill with further thoughts on such a comparison, but which he never completed. What he wrote instead is the scheme for a treatise on light and 15 The scheme of the book is: Book One on the light and shadow of opaque bodies; shadows in seven books. Book Two on primary shadows (ombre originali); Book Three on derivative shadows (om- bre derivative); Book Four on tanto vari effetti of derivative shadows—that is, on their re- Leonardo planned to start his treatise with a Proemio, which he drafted flections; Book Five on reflections of luminous rays in derivative shadowsreflesso ( concorso twice. He wrote the first draft: «Avendo io trattato delle nature de ombre of luminosi razzi and ombre derivative); Book Six on colored reflections; and Book Seven e loro percussion, ora tratterò de’ lochi, i quali da esse ombre tocchi fieno, on variations of colored reflections due to distance. See C. Pedretti,Commentary to: The e di loro curvità o obbliquità o diritti o di qualunque qualità trovare per Literary Works of Leonardo da Vinci by J. P. Richter, 2 vols., Berkeley/Los Angeles 1977, vol. 1, pp. 151-155; and Leonardo, Codice Atlantico, fol. 676r: «Parendo a me le ombre essere di me si potrà». As soon as he finished the initial draft, he thought of a better somma necessità in nella prospettiva, però che sanza quelle i corpi oppachi e cubi male wording. He thus crossed out the drafted Proemio and replaced it with a furono intesi – quello che dentro a’ sua termini collocate fia – e male e sua confine intesi new version immediately underneath: «Parendo a me a soffizienzia avere fieno, se essi non terminano in campo di vario colore da quello del corpo, e per questo io trattato delle nature e varie qualità delle ombre originali e derivative e lor propongo nella prima proposizione dell’ombre e dico in questa forma, come ogni corpo percussioni, tempo mi pare oramai di dimostrare li vari effetti de’ vari oppaco fia circundato e superfizialmente vestito d’ombre e di lumi, e sopra questo edifice il primo libro. Oltre a di questo esse ombre sono di sé di varie qualità d’oscurità, perché lochi, i quali da esse ombre tocchi saranno». da varie quantità di razzi luminosi abbandonate sono, e queste domando ombre originali, perché sono le prime ombre che vestano i corpi, dove appiccate sono: e sopra questo edificherò il secondo libro. Da queste ombre originali ne resulta razzi ombrosi, e quali si vanno dilatando per l’aria e sono di tante qualità, quante sono le varietà dell’ombre origi- stra che se ‘l punto n solamente vedessi, ch’l primo obbietto f occuperebbe all’occhio tutta nale donde si derivano, e per questo io chiamo esse ombre, ombre derivative, perché da al- la parte b c del secondo obbietto. Ancora si conferma tutte le spezie delli obbietti entrare tre ombre nascano: e sopra di questo io farò il terso libro. Ancora queste ombre derivative nell’occhio sottosopra: dopo f vedi b di sopra essere di sotto in n e e di sotto rispondere di nelle loro percussioni fanno tanti vari effetti, quanto son vari lochi dove esse percotano: e sopra in o». Later, in the margins of this long paragraph, Leonardo added a small sketch qui farò il quarto libro. E perché la percussion della dirivativa ombra è sempre circundata and a note on perspective, which further elaborates on the size of an object in relation da percussion di luminosi razzi, la quale, per reflesso concorso risaltando indirieto verso to the distance between the eyes (interpopille): «Prospettiva. Ogni corpo maggiore delle la sua cagione, trova l’ombra originale e si smista e si converte in quella, alquanto varian- interpopille [the distance between the two pupils], che dall’occhio debbe esere guidicato, dola di sua natura: e sopra questo edificherò il quinto libro. Oltr’a di questo farò il sesto sará distante 4 volte la sua grandezza. E se sia minore che lo interluce, nessuna cosa sara libro, nel quale si chiederà le varie e molte diversificazioni delli risaltanti razzi reflessi, i piú visina dall’occhio compressa, se 4 volte a distanzia dello intervallo delle popille non quali varieranno la originale di tanti vari colori, quanto fien vari i lochi, onde essi reflessi fia antiposta infra l’occhio e la cosa da esso veduta». razzi luminosi derivano. Ancora farò la settima divisione delle varie distanzie che fia infra 14 On the Paragone, see C. Farago, A critical interpretation of Leonardo da Vinci’s Para- la percussion del razzo reflesso al loco donde nasce, quanto fien varie le similitudine de’ gone, with a new edition of the text in the Codex Urbinas, Leiden 1992. colori che esso nella percussion al corpo oppaco appicca».
278 279 francesca fiorani leonardo’s optics in the 1470s object». In this folio, Leonardo did not mention Alhazen. However, fol- lowing the long passage describing his book, he traced a diminutive sketch of the head of man that bears the common attributes of a non-western savant—a beard and a conic hat. The outline of Leonardo’s book on optics does not correspond to any of Leonardo’s surviving manuscripts, but many of the issues he intended to discuss in it are present in Manuscript C, an unusually large notebook characterized by some carefully designed pages that gives us some sense of what Leonardo had in mind around 1490.
Manuscript C, fol. 6r On folio 6r of Manuscript C, Leonardo debated how objects come to be perceived correctly: «nessun evidente corpo po’ da li umani occhi es- sere ben compreso e ben giudicato se non per la varietá de’ campi, dove li stremi d’essi corpi terminano e confinano» (fig. 4). He then delved into an analysis of the errors of sight that occur in candlelight, and specifically discussed how candlelight and its glow, seen from afar, remain visible when a stick is placed in front of the eye. Leonardo explains:
Se l’occhio riguarda il lume d’una candela, lontano 400 braccia, esso lume apparirà a esso occhio, suo riguardatore, cresciuto 100 volte la sua vera quantità. Ma se gli poni dinanzi un bastone alquanto più d’esso lume grosso, esso bas- tone occuperà quel lume che pareva largo braccia 2. Adunque questo errore viene dall’occhio che piglia le specie luminose non solamente per il punto della luce, ma etiam con tutta essa luce. E di questo assegneremo la ragione in altro luogo16.
From this note, it is clear that Leonardo considered the surface of the eye instrumental to the perception of blurred edges, glows and reflections, which are, in turn, crucial to judge «la varietá dei campi dove li stremi d’essi corpi terminano e confinano»—that is, crucial to judge the location (situs) of objects within their surroundings. In other words, in this passage Leon- 4. Leonardo da Vinci, Manuscript ardo not only established the relational nature of sight based on distance, C, 1490 circa, Paris, which is foundational to linear perspective, but he also argued that the cor- Bibliothèque de l’Institut de France, fol. 6r
16 Leonardo, Manuscript C, fol. 6r. The two drawings in the upper part of the page illustrate this same text, since the text next to them refers to a different topic, the «moto dell’aria e dell’acqua».
280 281 francesca fiorani leonardo’s optics in the 1470s rect perception of things depends on the relation of light and shade with their full beauty»17. It does remain suggestive, however, to read Alhazen’s surrounding elements. Leonardo said that he would explain le ragioni of examples along Leonardo’s paintings. this phenomenon elsewhere, in altro loco. Codex Atlanticus, fol. folio 676r- For example, for Alhazen the range of moderation of the medium— v, which relates chronologically, thematically and physically to Manuscript when air becomes so hazy that it obfuscates the correct perception of an C, is a plausible candidate for such altro loco. object— depends not only on distance but also on the «subtle features» of Leonardo’s reference to the surface of the eye and to «this error that the object because «a visible object that possesses no subtle features will comes from the eye» (questo errore [che] viene dall’occhio) brings us closer be correctly perceived by sight in air that is hazy enough that another vis- to Alhazen, specifically to his errors of sight. ible object possessing subtle features will not be perceived through it in a determinate way»18. Alhazen applies similar reasoning to the perception of smallness: «the range of moderation for distance depends not only on color, leonardo and alhazen but also on the tiny features that are in the body, as well as on the light and the six other conditions that have been mentioned»19. One wonders if According to Alhazen, errors of sight depend on many variables: the such thinking informed Leonardo’s decision to revise the background of distance between object, viewer and light source; their reciprocal orienta- his paintings in the 1470s, especially in the cases of the Annunciation and tion; their size; the quality of their bodies; opacity; the transparency of the the Adoration of the Magi. In these instances, Leonardo drew elaborate medium; and health of the eye. For each «error of sight», Alhazen recom- details on the gesso preparation in the background—a marine view in the mended a «range of moderation», or a range within which knowledge is Annunciation and groups of people in the Adoration—but decided against certain, but outside of which sight errs. His many examples make it clear elaborating many of these details further. He instead covered them with that this range of moderation is never absolute, but is rather determined a layer of imprimitura and eliminated them from the final painting. Did case by case, in relation to the range of moderation of other variables. he judge these details too small to be visible in the conditions that he had For instance, for Alhazen, the best light for judging an object is moderate imagined? light—neither too faint nor too brilliant—but the limits of that range— Another of Alhazen’s major concerns is the transparency and color of how moderate light should be—change in any given situation depending the medium, which he illustrates with examples pertaining to textiles and on the distance of the light from the viewer and from the object, its ori- colored glasses: How does the color of a cloth appear if seen through the entation toward both viewer and object, and on the size and color of the threads of another textile? Do the two colors mingle or remain separate? light itself, the size of the object, the amount of details the object contains, And how does the color of the skin appear under a cloth? Alhazen offers its color, the thickness of the medium, and so forth. The range of mod- intricate explanations of the narrowness of the threads, the size of the in- eration for each condition is particularly important to the perception of terstices, the colors of fabrics, distance, light source, and so forth20. Is it distance, which is never immediate but always mediated, meaning that it possible that such reasoning also lies behind Leonardo’s attention to the is always achieved through cognition, which is, in turn, based on intuitio transparency of drapery and glass, which is documented from his early Ma- and aspectus. donnas onward? The Madonna of the Carnation may be read as a tour de Interestingly, Alhazen often illustrated the limits of the range of mod- force of transparency in its representation of different objects and mediums: eration with examples taken from painting, and he referred specifically to the medium of air and the texture of hair, cloths and fur, or the details of an object. Kemp has perceptively remarked that Leonardo did not wish to 17 Kemp, 1993 (as in n. 4), p. 158. depict Alhazen’s errors of sight; rather he wished «that lighting conditions 18 Alhazen, De aspectibus, Book iii, 3.10. should generally be contrived to fall within the “range of moderateness” so 19 Ibid., Book iii, 3.15. that the modeling of form and the colors of surfaces should be visible in 20 Ibid., Book iii, 6.18-22.
282 283 francesca fiorani leonardo’s optics in the 1470s the magnificent glass vase in the foreground, perhaps inspired by northern examples; the atmosphere visible from the windows that renders the moun- tains indistinct; the texture of different fabrics—including, velvet, silk and gauze—that becomes more transparent as the years go by (fig. 5). To explain errors in the perception of roughness (asperitas), or texture, Alhazen resorts again to painting, specifically to the appearance of hair:
The hair of someone who is depicted in a painting that is viewed at an inor- dinate distance is judged to have texture because that texture is represented by the painting. Since it is known that real hair has texture, the soul concludes by resemblance that the painted hair has texture according to the way their form is represented. The same error occurs in the case of clothing with designs and with the hair of animals that are represented in paintings21.
The opposite of asperitas is the perception of smoothness, which Alha- zen illustrates with another reference to painting:
There arises an error in the judgment of texture in the painting because of the inordinate distance in relation to the object that is painted. For the smoothness of a painting cannot be perceived unless it is quite distinct; hence, a moderate distance with respect to other things is inordinate with respect to the apprehen- sion of smoothness22.
Alhazen’s long list of examples of misperception has been regarded as the least original part of his work23. But it is also here that Alhazen makes concrete the principles of color perspective and visual acuity and where he explains how the propagation of light is always imbued with the propagation of color and of medium. These are the very principles that inform what Leonardo would later call prospettiva di colore and prospettiva di spedizione24. 5. Leonardo da Vinci, details of Benoit Madonna (1480 circa), St. Petersburg, Hermitage; Drapery 21 , Book iii, 7.39. Ibid. around the leg of a seated 22 Ibid., Book iii, 7.43. figure (1507-1510), Paris, 23 Smith, 2001 (as in n. 8). Musée du Louvre; 24 It is important to remember that Alhazen, his medieval followers and Leonardo did Virgin and Child with not distinguish between hue and tone, and so whenever Leonardo discusses lights and St. Anne (1510 circa), shadows he also discusses colors, whether he makes this explicit or not. Paris, Musée du Louvre
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For Leonardo, Alhazen’s errors of sight did not simply provide a cata- vives in the Vatican Library25. Although it remains unknown who did the logue of visual effects, or the principles of color perspective and prospettiva translation, the fact is that sustained interest in Alhazen’s original writings di spedizione, or even a basis for the range of moderation. Alhazen’s er- —rather than the interpretation provided by his Christian medieval fol- rors of sight supplied Leonardo with a framework for testing the limits of lowers (Bacon, Witelo and Pecham)—is registered in Italy from the late the range of moderation. He created images that not only fall within the fourteenth century onward. «range of moderation», but also at the limits of that range. In other words, Biagio Pelacani da Parma, a professor of mathematics at the university a minimal variation would put the image outside the range of modera- of Pavia who had spent sometime also in Florence, was among the experts tion and the experience provided by the painting would be ambiguous, on Alhazen26. In his Questiones super perspectiva Pelacani shared Alhazen’s its perception would be erroneous and it would determine misperception view that sight never errs, but he further stressed that knowledge is never rather than knowledge. At the same time, these images at the limit of the perfect since it is constantly revised in light of new sensory data, a po- range of moderation stretch the eye, forcing it to participate in an active sition that seems even closer to Leonardo’s. Although it was written in and continuous process of recognition from the universal to the particular, Latin, Pelacani’s Questiones, of which numerous fifteenth-century manu- moving back and forth between intuitio and aspectus, and also subject- script copies survive in Florentine libraries, was generously illustrated, and ing to judgment the peripheral areas, where derivative shadows and their it was divided into the traditional three parts of optics: direct, reflected and colors are projected, the areas indispensable for knowing things, the areas refracted vision. Pelacani also addresses topics that earlier authors consid- captured on the surface of the eye. ered beyond the domain of theoretical optics, such as burning mirrors, the At a deeper level, Leonardo’s paintings mimic what Alhazen called the rainbow and other optical illusions, all themes that appealed to a broad process of certification—an intense back and forth between sensory data public of craftsmen. For Leonardo—and fifteenth century art theory more and judgment, sight and soul. Unable to certify what sight sends in, the generally—it is Pelacani’s discussion on composition that is particularly soul repeats its operation indefinitely, over time, until it reaches certifi- interesting. cation. Leonardo’s images force repeated scrutiny, repeated validation of Alhazen had discussed composition in relation to letters and inscrip- sensory data to achieve knowledge. This certification applies to the entire tions, but Pelacani extended that discussion to three-dimensional images. painting, its setting, landscape, figures, and, above all, to gestures and ex- For Pelacani a two-dimensional image, which he called figura superficialis, pressions, the means of visualizing the motion of the mind. Optics for is known through the perception of size (magnitudo), but a three-dimen- Leonardo works both at the level of art making—that is, at the level of sional image, which he called figura corporalis, is perceived via composition figuring out painterly techniques to represent images at the limit of the (in compositione)27. Beauty is likewise perceived in compositione. Pelacani’s range of moderation—and from the point of view of a theory of knowl- edge—that is, how viewers react to an image emotionally. How and when Leonardo read Alhazen remains unclear, but unques- tionably the optical principles of color perspective and prospettiva di 25 G. Federici Vescovini, «Contributo per la storia della fortuna di Alhazen in Italia: il spedizione were already operative in Leonardo’s works of the 1470s. At the volgarizzamento del MS Vat. 4595 e il Commentario terzo del Ghiberti», in: Rinascimento, same time, Alhazen’s writings were available in the vernacular. v, 1965, pp. 17-49. 26 Edgerton, 1976 (as in n. 4). See also: Filosofia, scienza e astrologia nel Trecento eu- ropeo. Biagio Pelacani Parmense, ed. by G. Federici Vescovini, F. Barocelli, Padova 1992; G. alhazen in the vernacular Federici Vescovini, Astrologia e scienza: la crisi dell’aristotelismo sul cadere del Trecento e Bi- agio Pelacani da Parma, Firenze 1979; Federici Vescovini 1965 (as in n. 8); Blaise de Parme, Quaestiones super perspectiva commini, ed. by G. Federici Vescovini, J. Biard, Paris 2009. Alhazen’s De aspectibus had been translated into Italian as Degli aspetti 27 Pelacani: «figura superficialis repetitur in magnitudine, figura corporalis seu solida sometime in the fourteenth century and a copy of that translation sur- in compositione» (quoted in Federici Vescovini, 1965 [as in n. 8], p. 259).
286 287 francesca fiorani leonardo’s optics in the 1470s terminology seems pertinent to Alberti’s De pictura, a text that we usually liteca Riccardiana in Florence. Long ago, Alessandro Parronchi attributed read via Panofsky and Baxandall and whose optical precedents we tend to the manuscript to Toscanelli; more recently Eugenio Battisti assigned it forget. Alberti’s three parts of painting— circumscription, composition to Fontana29. It is impossible to confirm either attribution, but based on and the reception of light—which Baxandall correctly related to ancient the manuscript’s internal evidence, it can be confirmed that this vernacu- rhetoric, are equally inspired by medieval optics. For Alberti, just as for lar text is a drastically abridged and simplified version of Pelacani’sQues - Pelacani, the perception of an object as a solid does not only require the tiones. Beautifully illustrated, easy to read and addressed to an artist, this perception of magnitude, or circumscription, but also the perception of text eliminates complex demonstrations, abounds with practical examples distance and the perception of depression and relief, or composition. from reading glasses to gigantic light lanterns, and fancy optical devices for Another expert on Alhazen was Giovanni Fontana, the author of De dinner parties. It also stresses the importance of the medium. A recurrent omnibus rebus naturalibus, published in 1544 under the name of Pompo- example is how air affects the perception of two towers in the distance, nius Azalus, but written in the early fifteenth century. Fontana is an elusive which is exactly the example Leonardo chose to explain aerial perspective figure and the contour of his personality is uncertain. He declared himself (figs.6 , 7). The cultural significance of this vernacular text cannot be over- to be a student of Pelacani, but joined the university of Pavia after the stated. It closes the gap between the theory and practice of optics, between master had already died. Among other things, he wrote a treatise on per- practitioners who sought theoretical explanation for their practices and spective for his friend the painter Jacopo Bellini. This treatise is now lost, scholars who made their knowledge available to workshops. but Fontanta described it in another of his books: Perhaps the Italian translation of Alhazen’s De aspectibus, which made Alhazen’s writings potentially available to the larger non-Latin speaking Da questa esperienza naturale l’arte della pittura trae regole eccellenti com’ public, including an audience of artists, should be connected to that same ho chiarito con precisione in un’opera dedicata a Jacopo Bellini, insigne pittore circle of Pelacani and Fontana. Lorenzo Ghiberti read this translation in the veneziano, affinchè apprendesse anche come disporre i colori chiari e scuri in 1440s; it is not inconceivable that it remained accessible in artistic circles in maniera da ottenere che non solo le parti di una singola imagine dipinta sul piano later decades and that somehow Leonardo read it as well. It is equally pos- acquistassero rilievo ma che esse si potessero credere colte nell’atto di avanzare un sible, however, that Leonardo had access to Ghiberti’s Terzo commentario, piede o una mano e che ugualmente apparissero distare di miglia uomini, animali which incorporated extensive sections of Alhazen’s De aspectibus. e monti disposti ugualmente su una stessa superficie. Infatti l’arte della pittura (ars pingendi) insegna che si devono dipingere le cose più vicine con colori chiari, le lontane con colori oscuri e quelle poste a media distanza con color intermedi28. lorenzo ghiberti and alhazen Even from this brief description, it is clear that Fontana’s text did not As Gabriella Federici Vescovini has demonstrated, Lorenzo Ghiberti instruct artists in the rules of linear perspective, but rather in how to com- copied the Italian translation of Alhazen’s De aspectibus extensively in his pose (disporre) contrast of lights, shadows and colors, all themes that found so-called Terzo commentario, which in reality is not a commentary at all, their origins in Alhazen’s De aspectibus. but rather is a collection of excerpts from medieval optical writings that That Alhazen, via Pelacani, had some following in Renaissance Flor- ence is suggested by another manuscript in Italian now housed in the Bib-
29 Paolo dal Pozzo Toscanelli, Della prospettiva, ed. by A. Parronchi, Milano 1991; E. Battisti, G. Saccaro Battisti, Le macchine cifrate di Giovanni Fontana, Milano 1984. 28 Giovanni Fontana [under the name of Pompilio Azili], De omnibus rebus naturali- 30 Federici Vescovini (as in n. 25). See also: Der dritte Kommentar Lorenzo Ghibertis: bus quae continentur in mundo videlicet, Venezia 1544, fol. 74b (English translation in C. Naturwissenschaften und Medizin in der Kunsttheorie der Frührenaissance, ed. by K. Berg- Gilbert, Italian art, 1400-1500, Evanston/IL 1992, p. 175). dolt, Weinheim, 1988; Lorenzo Ghiberti, I commentarii, ed. by L. Bartoli, Firenze, 1998.
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Ghiberti copied verbatim30. What has not been fully appreciated is that Ghiberti quoted more passages from Alhazen than from any other optical writer and that Alhazen’s De aspectibus is the model Ghiberti adopted for his compilation (fig. 8). Ghiberti copied extensive parts of Alhazen’s theory of knowledge, including the passages on the formation of images on the surface of the eye, from which I started, and some of his errors of sight. Occasionally, he abandoned Alhazen’s text and followed instead the writ- ings of his Christian medieval authors. This seems to happen whenever Ghiberti sensed that their theories were more advanced than Alhazen’s, as in the case of the anatomy of the eye, which Ghiberti copied from Bacon. Indeed, Ghiberti’s selection of passages from different authors is far from random, revealing instead a critical approach to his sources, so much so that one is tempted to suggest that this selection was handed down to Ghiberti or that, at the very least, Ghiberti benefitted from an expert guide who was extremely well versed in the entire scholarship of medieval optics, and who would have been able to discern from the writings of Alhazen, Bacon, Pecham and Witelo the most original and advanced passages. Ghiberti departs from his optical sources in only one instance. When Alhazen discusses the perception of subtle details in different situations, he adds examples and comments derived from his own activity as a sculptor. Ghiberti’s selection would have provided a ready made collection of optical writings in the vernacular that highlighted Alhazen’s major contri- butions as well as the differences from his medieval followers. Leonardo may have had access to Ghiberti’s Terzo commentario via Bonaccorso Ghi- berti, Lorenzo’s grandson, who had inherited his grandfather’s writings. Ghiberti 6. Aerial perspective, Avicenna Florence. Biblioteca Not only were Leonardo and Bonaccorso exact contemporaries (they were Vitruvius Mediceo Riccardiana both born in 1452), but they also shared numerous interests, including Peckham (Manuscript 2110), in Brunelleschi’s machines. Drawings survive to document their common Alhazen fol. 22v Witelo interests and exchanges. Bacon 7. Leonardo da Vinci, The exact pattern of transmission from Alhazen to Leonardo may re- Aerial perspective, circa main undefined. Like Lorenzo Ghiberti, Leonardo might have read the ver- 1492, Paris, Bibliothèque nacular translation of Alhazen’s De aspectibus. Or he may have had access de l’Institut de France, Manuscript A (Manuscript to the vernacular manuscript based on Pelacani’s Questiones. Or perhaps he 2185), fol. 105v had access to Fontana’s now lost treatise on perspective. Or, most likely, he had access to Ghiberti’s Terzo commentario via Bonaccorso Ghiberti. 8. Chart showing the optical sources of Whatever the case, the note from Codex Atlanticus, fol. 847r, together Lorenzo Ghiberti’s with the optical effects of his early works, suggests that Leonardo might Terzo commentario have had access to Alhazen’s optical writings from a very early date. From
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Alhazen, Leonardo took the building blocks of his art theory, the opti- dominique raynaud cal explanation of the many phenomena that interested him as a painter, the model for his form of writing, which indeed came to resemble op- leonardo, optics and ophthalmology tical manuals rather than full-fledged humanistic treatises. Alhazen also provides a critical language for discussing Leonardo’s works, a system of values, concepts and notions that he shared. Leonardo strenuously sought to synthetize his own art theory to hand down to the next generation of painters, but he never achieved a coherent synthesis of optical theory and artistic practice. Or perhaps he did, and we have just looked for it in the wrong place, in the form of a complete treatise, a medium that remained always uncongenial to Leonardo, rather than on the surface of his painted images. introduction
Leonardo’s research on the eye and vision has given rise to opposing assessments, ranging from the apology of his explanation of how the eye works as a camera obscura to the most critical attitude. Historians of op- tics are usually reserved about his contribution. For David Lindberg, «his knowledge of the past optical tradition was very imperfect […] Leonardo’s view on ocular anatomy was exceedingly primitive—perhaps more primi- tive than those of any knowledgeable writer to touch on the matter from Galen to his own day»1. For Bruce Eastwood, «Leonardo used too few of the contributions of his predecessors […] and thereby was doomed to failure in any attempt to offer a unified theory of vision»2. Likewise, in his edition of Alhacen’s De aspectibus, Mark A. Smith says: «Leonardo’s discus- sion of image-inversion in On the eye reveals a fairly limited understanding of perspectivist concepts»3. All this is correct. But these negative assessments derive some of their strength from the fact that the practice of anatomy and linear perspective are well documented in Leonardo’s writing. Thus one expects him to have
1 D.C. Lindberg, Theories of vision from Al-Kindi to Kepler, Chicago 1976, pp. 156-162. 2 B.S. Eastwood, «Alhazen, Leonardo, and late-medieval speculation on the inversion of images in the eye», in: Annals of Science, xliii, 1986, p. 446. 3 A.M. Smith, Alhacen’s theory of visual perception. A critical edition, with English trans- lation and commentary, of the first three books of Alhacen’s De aspectibus, the medieval - - Latin version of Ibn al-Haytham’s Kitab al-mana.zir, Philadelphia 2001 [hereafter: Alhacen, 2001], p. cvi.
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