Since time out of mind, people have marveled at the mysterious Mona Lisa smile. Lovers of painting have reported for centuries that her smile changes before your eyes as if she were a living person.

I always assumed this was romantic hyperbole, but interestingly, it turns out to be demonstrably real. Moreover, it is not difficult to dissect the painting digitally and show how it works. The subtle blending of Leonardo’s famous sfumato technique is not simply a stylistic element. It is one-half of the mechanism that produces the unique mutability of the Mona Lisa smile.

In most cases I abominate the phrase, but in this special case, you really could say that the beauty is in the eye of the beholder because the technique takes advantage of the structure of the eye. Below, we’ll look at how the technique works at a semi-mathematical level, then dissect the image algorithmically to show the component parts and explain and how they are used to present the viewer with multiple versions of the image that the eye shifts between.

The code to do this is included in the article, along with hints about how to explore this mechanism farther.

I haven’t seen this explanation of the sfumato technique anywhere, but if someone else has pointed this out, please let me know.

Continue reading “That Mona Lisa Smile” →