In the early 80’s I was a chemistry graduate student, and a professor asked me to serve drinks at the annual meeting of the American Chemical Society. In return, I could sit through the sessions and listen to the speakers. When I found out that one was going to report on the latest studies on the shroud, I immediately volunteered. To make a very long story short, the scientist claimed that the markings on the shroud (other than the blood) were caused by some form of energy that we had no knowledge about. He ended up his talk by saying that, in his opinion, the only explanation was that something happened to the shroud when Jesus rose from the dead. Not bad, for someone who called himself an agnostic.
Just one example:
The Shroud of Turin didn't get much publicity prior to the 19th Century because it wasn't subject to the scrutiny of modern technology. What changed this was the advent of photography in the 19th Century. When the Shroud was photographed for the first time, it became clear that the Shroud itself is a photographic negative. For anyone to believe that someone in the Middle Ages fabricated such a thing -- hundreds of years before photography was even invented -- requires an enormous leap of faith (pun intended) that can't be supported by objective assessment of the subject.
This has always been my belief on how the image was created. An extremely bright suffusion of light and energy by a source we cannot begin to comprehend.