It was very difficult for him to dissect the muscles of the lips because the muscles here are tiny and numerous. During this experiment, da Vinci studied horses as well. He compared human expressions to that of horses. In the notes, he wrote, “Notice whether the muscle that raises the nostrils of the horse is the same as that which lies here in man.”
Hardly, throughout history, any other artist has dissected the faces of a horse and a human and done these experiments. His obsession with Mona Lisa’s smile didn’t end here. After this, he did research on optics as well. He found that the light rays don’t merge together into a single point on our eyes, rather they spread out over the entire retina.
The centre of the retina, known as the Fovea, helps us see the finest details. On the other hand, the rest of the retina picks up shadows and black-and-white imagery more. Using this knowledge, he focused on the shadows in such a way that even when you see the Mona Lisa in your peripheral vision, as in, if you are looking this way and Mona Lisa is on the other side, even if you are not paying attention to Mona Lisa, the effect of her smile is still there.
When you look at her smile closely, you will see that its central line is a flat line, is why when you look at her smile, it looks like she is not smiling at all. But on the other hand, the shadows created using the Sfumato technique, have such an effect that when you look elsewhere, your peripheral vision sees that smile and its shadows are reflected. And then you feel that Lisa is smiling.
