The Adoration of the Shepherds, Matthias Stom (also called Stomer); oil on canvas, I don’t have size information; link is to zoomable image on Google Art Project, high-res downloadable file on Wikimedia Commons; original is in the Palazzo Madama, Turin.
Stom was a 17th century Dutch (or Flemish) painter known for his paintings done in Italy, where he became influenced by the work of Caravaggio and his followers.
He did at least three different versions of this scene. In all of them, the child is the source of light, throwing the other figures into high relief against the dark background with a dramatic chiaroscuro characteristic of Caravaggio.
I like this one in particular, with the interesting and strongly rendered faces of the shepherds, and the beautiful modeling of their hands.