Good grief, this keeps coming up.

The Man Behind the Shroud?
There is a very credible theory that Leonardo created the Shroud of Turin by a photographic technique. Could it be his face?

First of all, there are no silver or chromium-based substances on the Shroud. Chemically, it is not a photograph. Second, a photograph does create a height-field image (3D data). The image on the Shroud is a height-field. Third, Leonardo was born in 1452. The Shroud that is now in Turin was displayed in Lirey, France in 1356. Fourth, there is compelling evidence that the Shroud that is now in Turin was in Constantinople in A.D. 944 and Edessa as early as 544. (See: What is the history of the Shroud in the Greek-Byzantine Period?

Radio carbon dating of the fabric of the shroud places it a while before Leonardo’s birth so clearly in is a medieval fake as were many relicks. Leonardo wasn’t stupid; if he were to try to fake it he would have used old cloth so the dating is consistent.

I suppose that this was because he knew carbon dating was to invented 500 years later.

Leonardo da Vinci, Mona Lisa and the Shroud of Turin | World in Christ Christian Gathering Place