High-res 3D scan helps uncover `Mona Lisa' secrets

Scientists have made the most detailed copy yet of the most famous painting in the world, using a new three-dimensional high-resolution scan to look at the Mona Lisa in depth.

Canada's National Research Council (NRC) will use the 3D scan to reveal features invisible to the naked eye.

The technique should give scientists and art historians a new perspective on the painting and help them to uncover some of the mysteries surrounding Leonardo da Vinci's "sfumato" painting technique.

"We have made a virtual model of the painting so we can zoom in and look at features on the surface and back in great detail, in a way you really can't see on the real painting," said John Taylor of the NRC.

The project began in 2004, when curators at the Louvre museum in Paris brought in scientists to help create a virtual model of the painting.

"They wanted to document the painting and monitor its state of conservation as well as use these techniques to get more information on the materials and techniques of the artist," Taylor said.

The NRC team stitched together scans of the front, back and edges of the painting to construct their 3D model.

Once completed, the model could show up details as small as 10 microns -- a tenth of the thickness of a human hair.

The NRC's laser scanner used a low-power white laser spot to record the image. The resolution obtained is is equivalent in detail to a 113 megapixel photograph.

By comparison, today's commercially available digital cameras can only produce -- at most -- photographs of up to 14 megapixels.

The first objective was to record how the wooden panel on which the Mona Lisa is painted has warped over time -- by 12mm in the bottom half.

The detail in the 3D model also allowed researchers to examine the thin layers of paint that da Vinci used to make his masterpiece.

Da Vinci used a technique he called "sfumato" to paint the Mona Lisa.

This involves overlaying translucent layers of color to create perceptions of depth and volume so that there is no perception of transition between one color and another.