The Painting Style Called Sfumato

Leonardo da Vinci declared that nothing in nature has precise mathematical lines or borders. This sounds idiotic. In his biography of Leonarda da Vinci, Walter Isaacson says that the statement was based on a “Leonardesque blend of observation, optics, and mathematics”.

 

A line is of invisible thickness, ergo it followed that boundaries in nature must really be blurred. This was the origin of the sfumato, the technique of using hazy and smoky outlines in paintings.

 

Leonardo came to this conclusion via his study of optics. He wrote:

“If all the images which come to the eye converged in a mathematical point, which is proved to be indivisible, then all the things in the universe would appear to be one and indivisible.”

Rather, he (almost) correctly said:

“The visual faculty does not occur in a point; it is diffused throughout the pupil (actually the retina) of the eye.”

He came to this conclusion by moving a needle closer and closer to one eye. No matter how close it came, it never blocked the vision of the eye, as it would have if sight were processed in only a single point of the retina. Instead, the needle became a blurry, transparent fog.

 

To convey depth (distance) of objects within a painting, he understood the importance of perspective (objects shrink in a size the farther away they are). But he also realized that perspective alone wasn’t enough: Colors vary based on their distance from the eye. And lastly, the farther away an object was, the more blurred it should be in the painting. All of which is why Leonardo instructed:

“You must diminish the sharpness of those objects in proportion to their increasing distance from the eye of the spectator.”

Reduced sharpness. Blurred. That wasn’t just because of the way the eye works, he declared. The air and mist between the object and the eye also “prevent our seeing distinctly the minute parts of objects”.

 

All the above rules, he also realized, applied to paintings of normal sizes, i.e., ones in which the edges and the center of the painting are at practically the same distance from the viewer. But what about a fresco or a mural? One edge might be twice as far from the viewer as the center. Therefore, such large paintings require a mix of natural perspective and “artificial perspective”.

 

It’s amazing how many concepts Leonardo combined in theory and then went on to execute in practice to produce his masterpieces.