Author(s) Cousin, Jean
Title Livre de perspective
Imprint Paris, J. Le Royer, 1560
Localisation Paris, Ensba, Masson 403
Subject Geometry, Perpective


     Jean Cousin (1490?-1560?), a painter from Sens who had settled in Paris around 1540, made many drawings which were used as models for stained glass windows, tapestries and engravings; he was also a geometer. His treatise on perspective which appeared in 1560 has not come out in a new edition since then, except in a facsimile (1974). In any case, it was mentioned in inventories after the death of several artists and in works dating from the end of the 16th and the 17th century, all of which proves a certain circulation in the artistic milieu. In a foreward, “Jehan Cousin au lecteur”, the author indicates a second volume devoted to the “figures de touts corps, mesmes des personnages, arbres, & paysages, pour entendre & cognoistre en quelle situation, forme & grandeur ilz doivent estre representez selon cest art” [of perspective], but he died before it could be published. Jean Cousin, the son, the author of a treatise on this subject, the Livre de Portraiture (1595, and regularly republished up until the 19th century), in which the individuals are drawn in perspective, probably reused a part of the material left by his father.
The Livre de perspective is rarely studied, and one often thinks that it apparently took up again, without adding anything new, the great principles of the traditional construction of an image in perspective: the lines perpendicular to the “ligne Terre” (the horizontal base of the plane) converge towards a point (the vanishing point) placed on the horizon; whereas the space between the lines parallel to the “ligne Terre” steadily decreases. In the De artificiali perspectiva (Toul, 1505) Jean Pèlerin, also known as Viator, perfected a method based on two “tiers-points” equidistant from the vanishing point, on the horizon line, to calculate the decreasing depths of the parallel lines. This method was adopted and perfected by Jean Cousin, who gave new geometric rigour to his account.
The Livre de perspective, made up of 58 chapters (141 unnumbered pages), follows a plan in three parts: the putting in perspective of plane figures, then figures in three dimensions, finally come examples of edifices, stairways, columns, and geometric volumes (among which are the “cinq corps réguliers” mentioned in Plato's Timaeus, in Euclid or in Dürer's Underweysung der messung, 1525). Cousin's plan is simple and rigorous: he states problems of increasing difficulty and considers several cases each time. The clarity of his demonstrations stems from the book's large format, and from the elegance of the sketches (drawn by the author himself on wooden plates to be engraved), in which letters allow one to refer easily and quickly to the explanatory text .
The most important one of Cousin's innovations in relation to Viator's method consisted in distinguishing between two different sorts of planes to draw a figure in perspective. One of these two planes is drawn above the other: the géométral plane, that is to say orthogonal, in which the figures undergo no optical deformation; and the perspective plane, determined by the vanishing point and the two “tiers-points”. One obtains a drawing in perspective by transferring the coordinates of the figure determined in the orthogonal plane. .
In Viator's tradition, Cousin gave preference to the question of the “tiers-points”, that is to say calculating the reduction of spaces in depth. The first rule of the treatise “demonstre la source & origine de cest Art de Perspective […], car par icelle vous sera monstré comment il faut extraire toutes profonditez & longitudes”. And the last rule focuses on two demonstrations exclusively concerning the “profonditez”, one backed up by an optical experiment, the other by a geometrical figure in which circles and squares alternate. It was traditionally used in mathematical works. The importance given to “tiers-points” could seem surprising today when studies often concentrate on the vanishing point. But for a novice draftsman, to whom the Livre de perspective was aimed, setting the vanishing point did not mean any great difficulty, any more than making perpendicular lines converge towards it. On the other hand, the “tiers-points” which define the reduction of parallels in depth are handled more delicately, and their effect on the point of view adopted by the representation is more complicated to explain. Thus Jean Cousin does not suggest a theory of perspective, but he wants to adapt to the painters' needs and he claims to regulate their practice.
Through his rigorous approach, Jean Cousin contributed in imposing the idea that the construction of an image in perspective responds to a corpus of geometrical rules which must all be systematically imposed. Thus he participated in a scientific reevaluation of perspective.

Valérie Auclair (Université Paris-Est, Marne-la-Vallée) – 2005

Critical bibliography

V. Auclair, Dessiner à la Renaissance. La copie et la perspective comme instruments de l'invention, Rennes, Presses Universitaires de Rennes, 2010.

V. Auclair, "La Quadrature dans le livre de Perspective de Jean Cousin (1560). Réflexions sur l'histoire d'une notion", M. Bleyl & P. Dubourg-Glatigny (ed.), Quadratura: Geschichte, Theorie, Techniken, Berlin/Munich, Deutscher Kunstverlag, 2011, pp. 65-80.

C. Grodecki, Documents du Minutier central des notaires de Paris. Histoire de l'art au XVIe siècle, Paris, Archives nationales, 1985-1986. 2 vol.

G.-M. Leproux, La Peinture à Paris sous le règne de François Ier, Paris, PU Paris-Sorbonne, 2001.

H. Zerner, L'art de la Renaissance en France. L'invention du classicisme, Paris, Flammarion, 1996.