There are four properties, which I call the STAR properties, that are also mystifying. These properties deal with how the image was created. The STAR properties have to be satisfied collectively by any image process and that’s a very, very tall order.
The shroud image is ephemeral. It only penetrates into a miniscule portion of the fibers, called fibrils. Microscopic examination of these fibrils shows that the image only penetrates the first 200-300 nanometers of the fibers. One nanometer measures one billionth of a meter.
Using a VP-8 image analyzer as well as linear scans, the image has been shown to render a convincing three-dimensional representation of the human body.
Another mystifying property is that the image is similar to those produced by half tone printing. Those qualities are variations in image lightness and darkness and the same color density.
Most processes in nature are isotropic, that is they spread out pretty evenly in all directions. Natural processes tend to produce fuzzy images that are blurred. The fact that the shroud image is not blurred, and is relatively high resolution means that the image is not isotropic, but parallel in a direction that is likely vertical.