Judas' cuff partially conceals the traitor's infamous bag of money; a close-up reveals more. View Slideshow 
MILAN, Italy -- A 16-billion-pixel image of Leonardo da Vinci's The Last Supper -- said to be the world's highest-resolution photo -- went online Saturday, making the masterpiece available for scrutiny by art lovers everywhere.
White-robed Dominican monks opened the doors of their sacristy to unveil the high-res image of the painting on a giant screen just steps away from the real thing at the church of Santa Maria delle Grazie.
The digitized version, produced using special techniques designed to protect the fragile painting from damaging light exposure, gives anyone with an internet connection a chance to dig deeper into Leonardo's techniques than ever before.
With the air of chiding an old friend, Leonardo expert Pietro Marani zoomed in on the cuff of traitor Judas to show the gold flake Leonardo applied.
"He went against his own better judgment here," Marani said. "We know he considered using real gold a cop-out, that he thought true artists should be able to make paint glitter like gold, but there it is."
For a close-up on the workings of a genius, Marani recommended viewers search the Last Supper for the church bell tower and shrubs outside the windows, the patterns and wrinkles in the tablecloth, the reflection of an orange wedge in a pewter plate in front of Matthew and the perspective lines in the upper left-hand corner that lead (imperfectly) to Jesus' eye.
Technicians at HAL9000, a company specializing in art photography, faced a number of challenges in capturing the 15th-century depiction of the moment when Jesus tells his apostles that one of them will betray him.
Leonardo used oil and tempera paints on dry plaster, an experimental technique, and as a result, the Last Supper is now so faded and cracked it can't withstand exposure to bright light. To protect the painting, HAL9000 worked with restoration specialists at Rome's Istituto Centrale per il Restauro to develop a lighting system without the ultraviolet emissions and high thermal impact so hazardous to works of art. Shot with a Nikon D2X digital SLR in just nine hours, the total impact of the digitization process was equal to just a few minutes of the soft lighting that normally illuminates the painting.
Back in their office, technical supervisor Mauro Gavinelli and his team stitched together 1,677 panoramic images of the 15-foot-by-29-foot painting using two quad-core AMD Opteron processors, 16 GB of memory and a 2-terabyte hard disk.
In the late 1400s, Leonardo painted the Last Supper, called Il Cenacolo in Italian, to provide monks at Santa Maria delle Grazie something to contemplate during meals. Father Stefano Rabacchi, the current prior of the monastery, said that although the work was originally painted just for them, they are obliged to share it with the world today.
Some 320,000 tourists troop in every year to see it, often reserving tickets for a 15-minute viewing months in advance. Visitors pass through a decontamination chamber, 25 at a time, where some of the city smog is sucked from their clothes.
Concerns about the fading mural's health were raised again when Italian daily Corriere della Sera reported Friday that PM10 levels in the church's dining hall have tripled in the last two years, raising concerns about how long the work will ultimately stay open to the public.
An filtration system removes up to 70 percent of the pollution from the chamber, said curator Alberto Artioli, adding that doors won't close on the work any time soon.
For those not able or willing to come to Milan, will a virtual visit surpass the actual painting?
"It's exciting to see just how technology can show what you wouldn't normally be able to see," said Vincenzo Mirarchi, HAL9000's general manager. "But it's not meant to substitute for the real thing. Seeing it on a computer screen will never be the same as standing in front of Leonardo's work."
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