On the Nature of the Background behind Mona Lisa

100 words One of the many questions surrounding Leonardo’s Mona Lisa concerns the landscape visible in the portrait’s background: Does it depict an imagination of Leonardo’s mind, a real world landscape or the motif of a plane canvas that hung in Leonardo’s studio, behind the sitter? By analyzing divergences between the Mona Lisa and her Prado double that was painted in parallel but from another perspective we found mathematical evidence for the motifcanvas hypothesis: The landscape in the Prado version is 10% increased but otherwise nearly identical with the Louvre one, which indicates both painters used the same plane motif-canvas as reference. When the conservators of the Museo Nacional Del Prado in Madrid were asked by the Louvre to lend them their copy of “La Gioconda” to be presented in a special exhibition in 2012, they started to inspect the painting closely. Though the Prado’s Gioconda and the Louvre’s original Mona Lisa both depict a similar looking young lady in about the same pose, their resemblance was rather limited at first sight, particularly because of the dense black background of the Prado version. So it must have been kind of an “Aesthetic Aha!” [1] when the first infrared examination revealed a landscape hidden beneath the black color. In the course of the subsequent restoration, the black overpainting was removed and it became visible that the landscapes in the Prado’s Gioconda and the Louvre’s Mona Lisa do very much look alike (see Fig. 1). Using infrared and x-rays, the Prado’s conservators further analyzed and compared the portraits. They found that both share several corrections also in the tracing and lower paint layers why it is now assumed that the paintings were executed simultaneously in Leonardo’s studio [2]. On the perspective The high visual similarity of the Prado and the Louvre versions could additionally be confirmed by means of bidimensional regression analysis. Applying this method to compare the coordinates of corresponding landmarks in the two paintings (e.g., the tip of Mona Lisa’s nose), Carbon showed that the landmark configurations of the face areas do match to a degree of above 99.8% [3]. Still, there is a small systematic difference: The sitter is depicted from slightly different perspectives. As we revealed recently [4], this difference does not only allow for reconstructing the positions of Leonardo and the second artist relative to each other and the sitter, respectively. It also causes grounds for the hypothesis that the two versions together represent a stereo pair as the identified horizontal disparity between the two depictions of the sitter (about 69 mm) quite well reflects the perspectival difference resulting from human interocular distance. In fact, it is statistically not different (p=.13, n.s.) from the mean interocular distance of (Italian) Caucasians being approximately 64 mm [5]. Whether this was or was not intended by Leonardo is debatable indeed. Nevertheless, the Prado version and the Louvre version, generated in Leonardo’s studio about 330 years before Wheatstone invented the stereoscope [6], can be combined to an image of Mona Lisa that has obvious stereoscopic qualities. On the background The background is one of the much discussed aspects of Leonardo’s Mona Lisa. The issue is whether it depicts just something Leonardo had imagined or rather something real, be it a real-world landscape (e.g., the Val di Chiana [7]) or simply the motif of a plane canvas that hung in Leonardo’s studio behind the sitter. (The same question can also be asked with regards to the loggia, including balustrade and the columns to the right and left of the portrayed lady.) In order to obtain further insights concerning the background, we utilized the above mentioned logic of analysis [3, 4]: We defined so-called landmark points, that is unique pictorial properties (such as a specific tear-off edge of a mountain) to be found in the background of both versions. Fig. 2 displays the linear trajectories between corresponding landmarks in the Louvre version (start) and the Prado version. Black arrows indicate trajectories for the landscape; light blue arrows indicate trajectories for the loggia. Mere visual inspection of the trajectories reveals already that there is a constant pattern of expansion, except for a slight deviation concerning the upper left part of the mountainside. Most importantly, the expansion is not stronger for parts that seem to be nearer (e.g., the loggia should be the nearest while those bizarrely shaped higher mountains in the upper part of the painting should be the farthest). Following Gibson’s ecological Fig.1. La Gioconda/Mona Lisa: The Prado (left panel) and the Louvre (right panel)