Most analyses of this painting divide the canvas into two parts: on the right, the jewel-toned Holy family; on the left, a landscape in browns and greens. Unity in a painting is extremely important, since a thing is beautiful insofar as it is one. Here, the two parts are tied together by the shepherds, who (having just come from their work) enter the holy scene of the nativity.
The painting might also be divided into three parts, which reflects the role of St. Joseph. Notice that Mary stands out from the rest of the painting in robes of deep blues and reds. Next, note that the Christ child touches no figure except Mary, by the hem of her cloak. Indeed, she and Jesus could be figures in a painting of their own, and seem almost superimposed on this one.
But St. Joseph, in muted colors and in the background, links them to the rest of the painting. In fact, it is precisely because of his quiet colors and his depth in the painting that he pulls the brilliant Madonna and Child into the canvas. Thus, St. Joseph joins Mother and Child to the fervent shepherds and their world.
