Researchers have found a "Mona Lisa" painting in the Museo del Prado in Madrid that might have been painted by either Da Vinci himself or one of his students.

The original "Mona Lisa" painting can be found in the Louvre Museum in Paris.

Back in 2012, scientists determined that the "knock-off" was actually extremely close to the original painting found in Paris.

The researchers confirmed that the painting had the same mountain landscape background as the original "Mona Lisa," meaning there is a good chance Da Vinci created the painting.

"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.

Carbon and Vera Hesslinger of Germany's University of Mainz determined this perspective shift by looking at so-called trajectories, or the "paths from a distinctive point on the source," according to Live Science.

The researchers examined things like the tip of Mona Lisa's nose, to a target, or the observer's/ painter's eyes.

It turns out that the real painting and the Prado one were painted from slightly different perspectives.

The horizontal difference between the two paintings was about 2.7 inches, which is around the average distance between a person's two eyes, according to Live Science.

Carbon and Hesslinger believe the two paintings form a stereoscopic pair, which means when viewed together, they create a 3D image of the "Mona Lisa."

We may never know who created the Prado painting, but Carbon did confirm that Da Vinci "intensively worked on the 3D issue." 

"Mona Lisa" paintings on his property at the same time, and that he owned colored spectacles, Carbon said, according to Live Science. "(This) might indicate that he did not only (think) about the 3D issue theoretically but in a very practical sense in terms of experiments."

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