The Conversion of St. Paul. 1600-1601. 
"Caravaggio's technique, a high-contrast form of chiaroscuro known as tenebroso, achieves effects that bear an uncanny resemblance to Edgerton’s high-speed flash photography," such as Milk Drop Coronet (1936) 
"In 1600, soon after he had completed the first two canvases for the Contarelli Chapel, Caravaggio signed a contract to paint two pictures for the Cerasi Chapel in Santa Maria del Popolo. The church has a special interest because of the works it contains by four of the finest artists ever to work in Rome: Raphael, Carracci, Caravaggio and Bernini. It is probable that by the time Caravaggio began to paint for one of its chapels, The Assumption by Annibale Carracci was in place above the altar. Caravaggio's depictions of key events in the lives of the founders of the Roman See have little in common with the brilliant colours and stylized attitudes of Annibale, and Caravaggio seems by far the more modern artist.
Of the two pictures in the chapel the more remarkable is the representation of the moment of St Paul's conversion. According to the Acts of the Apostles, on the way to Damascus Saul the Pharisee (soon to be Paul the Apostle) fell to the ground when he heard the voice of Christ saying to him, 'Saul, Saul, why do you persecute me?' and temporarily lost his sight. It was reasonable to assume that Saul had fallen from a horse.
Caravaggio is close to the Bible. The horse is there and, to hold him, a groom, but the drama is internalized within the mind of Saul. He lies on the ground stunned, his eyes closed as if dazzled by the brightness of God's light that streams down the white part of the skewbald horse, but that the light is heavenly is clear only to the believer, for Saul has no halo. In the spirit of Luke, who was at the time considered the author of Acts, Caravaggio makes religious experience look natural." 
: Edward A. Shanken, Art and Electronic Media, p.17