Can A Simple Physics Error Cast Doubt On A da Vinci Painting?

It seems that the recent auction of a Leonardo da Vinci painting (for $450 million no less) has what everyone seems to call a physics flaw. It involves the crystal orb that is being held in the painting.

A major flaw in the painting — which is the only one of da Vinci's that remains in private hands — makes some historians think it's a fake. The crystal orb in the image doesn't distort light in the way that natural physics does, which would be an unusual error for da Vinci.

My reaction when I first read this is that, it is not as if da Vinci was painting this live with the actual Jesus Christ holding the orb. So either he made a mistake, or he knew what he was doing and didn't think it would matter. I don't think this observation is enough to call the painting a fake.

Still, it may make a good class example in Intro Physics optics.

Zz.