Leonardo Da Vinci's "Mona Lisa" painting may be part of the oldest 3-D artwork, say two visual scientists.
In 2012, scientists discovered that beneath layers of black paint, a seemingly insignificant "knock-off" of the "Mona Lisa" in the Museo del Prado in Madrid was in actuality very close to the original hanging in the Louvre Museum in Paris, revealing the same subject with the same mountain landscape background. That painting may have been painted by Da Vinci or possibly one of his students.
"When I first perceived the two paintings side by side, it was very obvious for me that there is a very small but evident difference in perspectives," study researcher Claus-Christian Carbon of the University of Bamberg in Germany wrote in an email to Live Science. "Maybe the view of a perceptual psychologist is highly sensitive for such tiny differences, but it is very clear that also persons who are not so strongly involved in perceptual sciences can see it easily after having received information on the change in perspective." [See Images of "Mona Lisa" Paintings in 3D]
Turns out, the real "Mona Lisa," or "La Gioconda," and the Prado cousin were painted from slightly different perspectives. Carbon and Vera Hesslinger of Germany's University of Mainz figured out this perspective shift by looking at so-called trajectories, or the paths from a distinctive point on the source, such as the tip of Mona Lisa's nose, to a target, or the observer's (or painter's) eyes. The scientists also asked people to estimate the perspective of the "Mona Lisa" sitter, something Carbon called a psychological assessment of the perspective.
"This is particularly clear if you observe the chair on which La Gioconda sits: In the Prado version, you can still see the end of the end corner of the chair at the background of the painting, which you cannot see in the Louvre version, because the painter of the Prado version looked at the' Mona Lisa' more from the left than the painter of the Louvre version," Carbon said.
The researchers then could recalculate the position the painters took relative to each other and to the "Mona Lisa" sitter in Da Vinci's studio. They found that the horizontal difference between the two paintings was about 2.7 inches (69 millimeters), which is close to the average distance between a person's two eyes. (When a person observes an object, each eye sees a slightly different perspective of the object, both of which are sent to the brain and transformed into the three-dimensional representation of the object that we "see.")
From these results, the pair thinks the two paintings form a stereoscopic pair, meaning when viewed together create an impression of depth, a 3-D image of the "Mona Lisa."
The finding "is accurate in its analysis of the images and interpretation of a possible intent at a stereoscopic representation of the hands area," Martin Arguin, of the University of Montreal, wrote in an email to Live Science, after looking through Carbon and Hesslinger's journal articles on the subject.