Infra red reflectography was used to reveal the underdrawing. Infra red can pass through some paint layers before it is reflected by the charcoal underdrawing making it much easier to see. In this image an alteration to the position of the thumb of the hand of Christ from the cartoon The Miraculous Draught of Fishes can be seen. Infra red also revealed that Raphael, surprisingly, did not use any squaring up lines to facilitate the underdrawing. He appears to have worked freehand directly onto the paper.