Mona Lisa's spolvero revealed.

• First-time evidence of the use of spolvero on the Louvre's Mona Lisa. • Visible-NIR spectrum processed with L.A.M. allows the observation of spolvero , unlike IR 2000 nm. • The effectiveness of the L.A.M. technique is demonstrated with a comparative test. On the request of the Louvre Museum, Mona Lisa 's portrait was digitised with Lumiere Technology's high-resolution multispectral camera. The data from this digitisation revealed for the first time the spolvero (a drawing transfer technique) of the portrait. These discoveries change the history of this iconic symbol of Western painting because they are proof that a preparatory drawing was employed. These discoveries were possible because the multispectral camera produces high-resolution images of 13 filters, including 3 IR filters with a high signal-to-noise ratio and optimal spatial resolution. The images are processed with the layer amplification method (L.A.M.), which amplifies weak signals and thus reveals new details. A test board was made to compare the L.A.M. with traditional IR reflectography. [ABSTRACT FROM AUTHOR]