The Shroud was considered by believers to bear an image of Jesus formed in some miraculous way and by skeptics to be no more than a painting on cloth. Not until Secondo Pia photographed it on May 28, 1898 was it discovered that the image on the Shroud was something much more inexplicable and historically unique than could be dismissed so easily.
Whatever else you believe about the Shroud of Turin, there is one remarkable fact that even the most incredulous skeptic must acknowledge: it is the first true negative image in all of history. If it is a 14th century fabrication, it predates the second negative image by over 500 years, but if it is a genuine artifact from the 1st century, by over 1,800 years!
Just this single fact alone should pique the interest of anyone who has any real scientific curiosity, regardless of their personal beliefs. But the Shroud seems to have been summarily brushed aside with extreme prejudice by many who claim to have a high regard for scientific study. Being also a venerated religious relic has put it into a kind of nether world in regards to serious consideration by most of those who consider themselves scientifically minded people.
But there are those in scientific professions who have taken an honest, objective look at the Shroud and have agreed that this is a very unique and inexplicable object that challenges popular assumptions about how a historical artifact like this must have come to be. In fact some of the most enthusiastic believers in the Shroud's authenticity are respected scientists who admitted to being very skeptical before they carefully examined the evidence for themselves.