From The Telegraph:
Hidden beneath a piece of Holland cloth that was sewn by nuns in 1534, after a fire had blackened parts of it, the reverse side of the shroud was fully scrutinised for the first time in 2002, when the 14ft linen was unstitched from the Holland cloth. The back surface of the shroud was photographed in detail.
"When I saw the pictures, I was caught by the perception of a faint image on the back surface of the shroud. I thought that perhaps there was more that wasn't visible to the naked eye," said Prof Fanti.
"Though the image is very faint, features such as nose, eyes, hair, beard and moustache are visible."
However, the enhancing procedure did not uncover the full body image as it appears on the front side.