The Secret of the Mona Lisa Smile: Mystery Solved? | NOVA | PBS

Anatomy and his painting technique explain in part how Leonardo infused the Mona Lisa with a lifelike quality. But to complete the illusion, he needed to explore another area of science. How humans see. Among the many aspects in which Leonardo was using his knowledge as a scientist to become a better painter is optics. It's basic geometry because when you have an object with parallel lines, they will seem to vanish into a point, which is called the vanishing point. Leonardo was fascinated by many aspects of how we perceive our world. He even studied the composition of air to determine how atmosphere affects the appearance of objects in the distance. Leonardo is trying to capture the complexity of the world, but how can you paint something that you cannot see, like the transparency of air? Leonardo not only looked at mathematical perspective, but he looked at how colors change as you get further away. How the sharpness of something changes as you get further away from it. And did Leonardo also discover tricks of perception to pull off the greatest illusion of all? That elusive smile. She's looking out and her smile is a reaction triggered by the arrival of somebody. This is the fiction that the painting tries to establish. The great artists know how to draw you in, but not to tell you what to think. They offer the tease. The ambiguity of Mona Lisa's smile is indeed part of her allure. How did Leonardo pull that effect off? That is a question that intrigued neurophysiologist Margaret Livingstone. She studies the human visual system, how our eyes and brain operate together to make sense of the world. As a neurophysiologist, I actually learn a lot from artists because they study how we see. I study how we see. A lot of good art takes advantage of the computations your brain makes by exaggerating things that your visual system finds important. Human vision is among the best in the animal kingdom. The center of our retina is packed with special photoreceptors that enable us to see details or sharpness. But away from the center, toward the periphery, there are fewer of those types of receptors. We can see movement, but not detail. Okay, now I want you to close your eyes. I'm going to put up two versions of the Mona Lisa, one accurate and one distorted. To illustrate, Livingstone enlists her colleague, Peter, to see if he can spot a fake Mona Lisa using just his peripheral vision. Okay, briefly open your eyes and look at the yellow spot and close them right away. And point to which is the accurate reproduction. Open your eyes and see whether you chose the correct one. Point at the real version. Can I keep that? Peter got only one of four Mona Lisas right. And Livingstone says that's not unusual. Most people don't know how bad peripheral vision is, because as soon as something happens in their peripheral vision, they look at it and then they bring the high-resolution part of their visual system onto it. In fact, our eyes are constantly moving, three times a second, filling in the details. The effect got Livingstone thinking. Could this explain why the Mona Lisa sometimes seems to be smiling and sometimes not? Using a photo app, she blurs the image, like in our peripheral vision. So I filtered the image in such a way that it would look like what you would see to your peripheral vision, knowing what I know about processing. The result? She's grinning from ear to ear. As you look at the Mona Lisa, your eye moves around the painting. When you look away from her mouth, it enters your peripheral vision and Mona Lisa appears to smile. But look directly at the mouth and the smile vanishes. She seems like she's alive, because she looks different, depending on where you're looking. Leonardo's paintings come alive because he understands human emotion, and because he has a good feel for the underlying science. That combination comes together year after year as he's doing the Mona Lisa, to make it such an interactive painting. Back at the Louvre, Cinzia Pasquali has removed the old yellowed varnish from Bacchus, uncovering the brilliant original colors. It reveals an atmospheric perspective that suggests Leonardo's touch. Taking off these layers of darkened and yellow varnish, we were able to rediscover the original forms, the quality of the blue. It's a wonderful blue, and we see how the painter represents these cities with that effect of humility, of what Leonardo called the atmospheric perspective. But Pasquali's investigation has also uncovered details like the harsh shading in the face, that don't show the characteristic sfumato fingerprint of Leonardo. I can't see the Leonardo touch. This is a little bit mechanical. This line for the shadow is so hard, you know? Leonardo don't do this. Pasquali and the team at the Louvre have solved a centuries-old mystery. The Bacchus cannot be attributed to Leonardo. But that doesn't mean he wasn't involved. Very often his apprentices are actually painting the picture, so he would conceive the general design of the work, and then the manual execution would be delegated to members of his workshop. The restoration has succeeded in bringing much of the original beauty back to this painting. But it also raises an intriguing question. Should the same thing be done to the Mona Lisa? You have to imagine that under that varnish, you could see a wonderful blue sky, probably also the face, the hands are more pink, like natural skin. If we could just take that varnish off, we could see it the way Leonardo really did it. But I think French governments have fallen for less cause than trying to take the Mona Lisa out of circulation and clean it. Perhaps there is another way. Could she be given a digital makeover? That is what Pascal Kant is trying to do. He has analyzed the Mona Lisa with a remarkably powerful camera and lights, which he demonstrates using a replica. We make the measurements in the basement of the Louvre, inside the laboratory. It's very emotional to have the painting in hands. Without the frame, you can look at this painting under this very intense light that reveals everything that you cannot see usually. Kant's extremely detailed scan of the Mona Lisa and his analysis of the optics and chemistry of paint reveal how the colors may have changed over time. It's not just the varnish that yellows and darkens, but the pigments and oil in the paint itself. Kant's challenge is to reverse engineer the effects of that aging. This is not just photoshopping it and messing around with the colors, which you and I could do and get tolerable results, but this is based on pigment analysis. First, Kant determines how much the varnish has darkened, and with his computer, peels it away. Next, he identifies what the color of each pigment would have looked like 500 years ago, and recreates them to see the colors just as Leonardo did. For example, we know that Leonardo made the sky with white lead and lapis lazuli. So we have a software that removes the wrong colors to obtain the genuine color. Then, pixel by pixel, Kant restores those colors. Suddenly, a greenish sky becomes brilliantly blue, and a bit of flush comes back to Lisa's cheeks. Finally, as the French say, voila. Suddenly she doesn't look like the submarine goddess. She looks as if she's in the fresh air, which is just terrific. Kant's restoration has brought Lisa back to life, at least digitally, closer to the state that Leonardo saw her. Allowing us all to see the painting's legendary beauty, and the science it took. The geometry and optics of perspective, the anatomy behind her face, and the sfumato soft lines, capturing the mystery and movement of life. But even with all the modern insights, the Mona Lisa is vastly more than the sum of her scientific parts. Pinning down exactly why we are so drawn to her, ultimately remains as elusive as her smile. Three years before his death, Leonardo was invited to France to live and work for the king. He crossed the Alps by horse or mule, carrying three paintings. Those paintings, including the Mona Lisa, now hang at the Louvre, where the doors are about to open on the 500-year blockbuster Leonardo exhibition, a celebration of a genius who fused together the worlds of art and science. Leonardo is an Italian Renaissance painter, but his genius is universal, and it speaks to everybody.