Leonardo Da Vinci. St. Jerome Praying in The Wilderness, begun Ca. 1482; unfinished.

“…The painting shows St. Jerome at prayer at the end of his life, a hermit in the wilderness, alone save for his lion companion—a common Renaissance subject. And yet it stands alone in its deeply moving, intimate depiction of the penitent saint in a moment of private reverie. As Jerome stares up at his crucifix, his spiritual struggle is plain to see, even though many passages of work show little more than the ground preparation on the wood panel, with hastily sketched outlines.”

“A close examination of the paint surface reveals the presence of Leonardo’s finger prints in the upper left portions of the composition, … Leonardo used his finger to distribute the pigments and to create a soft focus effect in the sky and landscape.”

More here and here.