On Painting

Book I is a leisurely introduction to the basic geometrical principles of painting. "I usually give my friends the following rule: the more rays are employed in seeing, the greater the quantity seen will appear. ... Furthermore, the extrinsic rays, which hold on like teeth to the whole of the outline, form an enclosure around the entire surface like a cage. This is why they say that vision takes place by means of a pyramid of rays. ... We must now speak of the median rays. These are the mass of rays which is contained within the pyramid and enclosed by the extrinsic rays ... from their contact with the surface to the vertex of the pyramid they are so tinged with the varied colours and lights they find there, that at whatever point they were interrupted, they would show the same light they had absorbed and the same colour. We know for a fact about these median rays that over a long distance they weaken and loose they sharpness. The reason why this occurs has been discovered: as they pass through the air, these and all other visual rays are laden and imbued with lights and colors; but the air too is also endowed with a certain density, and in consequence the rays get tired and lose a good part of their burden as they penetrate the atmosphere. So it is rightly said that the greater the distance, the more obscure and dimmed the surface appears. ... We call the centric ray the one which alone strikes the quantity in such a way that the adjacent angles on all sides are equal. As for the properties of the centric ray, it is of all the rays undoubtedly the most keen and vigourous. It is also true that a quantity will never appear larger than when the centric ray rests upon it. ... [A]s it is only a single surface of a panel or a wall, on which the painter strives to represent many surfaces contained within a single pyramid, it will be necessary for his visual pyramid to be cut at some point, so that the painter by drawing and colouring can express whatever outlines and colour that intersection represents. Consequently the viewers of a painted surface appear to be looking at a particular intersection of the pyramid. ... Painters prove this when they move away from what they are painting and stand further back, seeking to find by the light of nature the vertex of the pyramid from which they know everything can be more correctly viewed." Now the principles of perspective and the costruzione legittima. "Let me tell you what I do when I am painting. ... I decide how large I wish the human figures in the painting to be. I divide the height of this man into three parts. ... With this measure I divide the bottom line ... into as many parts as it will hold. Then I establish a point ... wherever I wish; and as it occupied the place where the centric ray strikes, I shall call this the centric point. The suitable position for this centric point is no higher from the base line than the height of the man ... for in this way both the viewers and the objects in the pa

Book I is a leisurely introduction to the basic geometrical principles of painting. "I usually give my friends the following rule: the more rays are employed in seeing, the greater the quantity seen will appear. ... Furthermore, the extrinsic rays, which hold on like teeth to the whole of the outline, form an enclosure around the entire surface like a cage. This is why they say that vision takes place by means of a pyramid of rays. ... We must now speak of the median rays. These are the mass of rays which is contained within the pyramid and enclosed by the extrinsic rays ... from their contact with the surface to the vertex of the pyramid they are so tinged with the varied colours and lights they find there, that at whatever point they were interrupted, they would show the same light they had absorbed and the same colour. We know for a fact about these median rays that over a long distance they weaken and loose they sharpness. The reason why this occurs has been discovered: as they pass through the air, these and all other visual rays are laden and imbued with lights and colors; but the air too is also endowed with a certain density, and in consequence the rays get tired and lose a good part of their burden as they penetrate the atmosphere. So it is rightly said that the greater the distance, the more obscure and dimmed the surface appears. ... We call the centric ray the one which alone strikes the quantity in such a way that the adjacent angles on all sides are equal. As for the properties of the centric ray, it is of all the rays undoubtedly the most keen and vigourous. It is also true that a quantity will never appear larger than when the centric ray rests upon it. ... [A]s it is only a single surface of a panel or a wall, on which the painter strives to represent many surfaces contained within a single pyramid, it will be necessary for his visual pyramid to be cut at some point, so that the painter by drawing and colouring can express whatever outlines and colour that intersection represents. Consequently the viewers of a painted surface appear to be looking at a particular intersection of the pyramid. ... Painters prove this when they move away from what they are painting and stand further back, seeking to find by the light of nature the vertex of the pyramid from which they know everything can be more correctly viewed." Now the principles of perspective and the costruzione legittima. "Let me tell you what I do when I am painting. ... I decide how large I wish the human figures in the painting to be. I divide the height of this man into three parts. ... With this measure I divide the bottom line ... into as many parts as it will hold. Then I establish a point ... wherever I wish; and as it occupied the place where the centric ray strikes, I shall call this the centric point. The suitable position for this centric point is no higher from the base line than the height of the man ... for in this way both the viewers and the objects in the pai

Alberti is one of the more readable of the 'classic' authors on Art, much less prone to gossip than Vasari and less convoluted than Cennini. That said, some of the text on geometry in book one can be a bit difficult to follow. Alberti also loves to name-drop, continually referring to antique painters, but this was expected at the time - the ancients lending authority and historical context. 'On Painting' gives the reader an insight into the tastes and philosophies that inform the arts. Most interesting to me, as a teacher of drawing, were the insights on the fundamentals of life drawing - such as positioning of the head relative to the feet, and the shifting of values becuase of the limitations of white paper (or paint) being the brightest 'light' available to the artist. the saying 'there is nothing new under the sun' comes often to mind - you will read many of Alberti's observations in any contemporary text. Much of this may seem irrelevant to the modern painter - for example, his comments on consistency in portrayal of the figure may have been more relevant in an age when lay figures were used and painting took hours, but nonetheless bring up key points for the thoughtful artist to consider, especially for those interested in traditional painting. Use this book in conjunction with a good pictorial survey of art history (or the internet), so that you can readily refer to the pictures he mentions. For more of my reviews and links on Old Master Drawings, visit http://drawsketch.about.com/od/oldmasterdrawing/