It's not an assumption, please watch this to understand why: https://www.youtube.com/watch?v=I4c4812XA9A
It's hard to believe that you find that video to be convincing proof. A man desperate to show that it is authentic came up with several tests that show several different dates over several hundred years and managed to create a similar image (that we're not really shown) with electricity and a dummy. They didn't even say that his similar eletrical image only colored the surface fibers even though that point was stressed over and over.
Interesting, though, the image of Jesus being resurrected a lot like Frankenstein's monster.
Also that image was created by Computer graphics artist Ray Downing by using information embedded in the shroud, please watch rather than making assumptions, it is well worth it: https://www.youtube.com/watch?v=WNJPJ4JwHeE
Haven't watched this one yet. I'm undecided on whether to, since there's not much point without being convinced the shroud is authentic. Does it have the same kind of dramatic music and narration?