One theory of the creation of the Shroud is that it was manufactured by Leonardo da Vinci in the first half of the 1490s at the probable behest of Pope innocent VII. The process of manufacture employed a primitive, quasi-photographic technique using the principle of the camera obscura and light-sensitive pigments available to Leonardo at the time. Recreations of the suggested technique by British and South African researchers have been regarded by critical authorities as lending support to this theory, initially suggested in 1994. Consult the following references . . .