In his “List of Evidences of the Turin Shroud”, Giulio Fanti and his co-authors include: “B13) The body image has the normal tones of light and dark reversed with respect to a photograph, such that body parts nearer to the cloth are darker.” At first sight this may seem reasonable, and explains the remarkable appearance of the Shroud negative, but on reflection, it isn’t true. It implies that the skin of ‘normal’ people has ‘tones’ which change according to their distance from the observer. As if the ‘tone’ of the ridge of the nose is brighter than its sides, and the tone of the cheeks adjacent, and that the tone of the cheeks darkens towards the ears. This is bizarre. And nonsense. This is clearly obvious by looking at a face in profile as well as face on. The alleged graduation of skin ‘tone’ on the frontal image is not visible from the side. As an explanation for the ‘positive negative’, the variability of ‘normal tones’ is wholly inadequate.
A negative, by ordinary definition, is a photographic phenomenon whereby the more light which impinges on a sensitive plate, the darker the discolouration. In a ‘normal’ photograph this light falls within the visible range of the electromagnetic spectrum, derives from a source or sources outside the subject, and is focussed, via a pinhole or lens, such that the light from a particular spot on the subject concentrates on a particular spot on the film, and is not scattered all over the place. This cannot be true of the Shroud. Light from a source or sources outside the body would have to have passed through the upper part of the cloth in order to reflect off the body, and to have reflected off the lower part of the cloth beside it, so the background of the Shroud would be darker than the body, not lighter. Even very diffuse light produces shadow, which according to most observers, is not detectable on the Shroud.
Alternatively we may wish to extend the spectral range, make the surface of the body the source of the light, and, in the absence of pinhole or lens (pace the literal photography hypotheses) demand that the light from any particular place is somehow directed vertically up or down, by an unknown process. This plunges us into the ‘science of the supernatural’, a variation of scientific method in which the presumptions which underpin a hypothesis derive from the supposed result of the hypothesis, rather than from conventional scientific knowledge. Thus the fact that in the absence of any focussing method the radiation must be collimated is based only on observation of the image, not on any known scientific process.
Still, let us attempt to clarify the type and source of the radiation that could have produced the image, ignoring the constraints of the regular behaviour of dead bodies. Visible light has been proposed, and so have infra-red, ultra-violet, and X-rays, and also sub-atomic particles such as protons. It is supposed to have originated at the surface of the body, the bones or the flesh. Most particularly, it is supposed to have attenuated in such a way that the intensity of the image relates closely to the alleged distance between the body and the cloth, and not to the surface properties, material, texture or colour.
Take visible light, which is absorbed by a very small depth of skin, so must have emerged from the surface, or very close to it, of the body. Not being reflected, there is no reason why the Shroud image should correspond to the colour of the skin, hair, lips, bruising or dirty marks on the body, but only the distance travelled through air. The difference in shade between the skin, hair, lips or any surface discolouration is not discernible. This is certainly not a negative as we know them. And anyway, light is not attenuated by air: a white wall is brighter than a grey wall even if it is much further away.
Consider the right cheek (as we look at the images below).
It is composed of two dark areas separated by a lighter rough triangle, which inverts to two lighter areas separated by a darker one. If the first image were a photographic negative, then the lighter, triangular area, might represent a large purpling bruise, and no doubt the swelling to go with it, as dark areas in vivo are represented as light areas on a negative. The alleged ‘positive’ of the second picture would show the true colouration of the cheek (at least in monochrome), a dark triangular bruise between lighter, undamaged, areas of skin.
Actually, of course, nobody thinks that. The dark areas of the first image are assumed to represent swellings, and the lighter triangle is undamaged skin. This is not characteristic of a photographic negative.
Something similar affects the possibility that the Shroud image represents X-rays, and that the bones of the fingers, in particular, are seen through the skin of the hands. Here is the relevant area.
Different authors have different concepts as to the source of the X-rays. In medical practice, X-rays are directed through the body, are partially absorbed by the denser material, and are received by the sensitive plate more or less attenuated. Where the X-rays pass through easily, the plate is darkened, and where they are trapped by bones, the plate is left white. This is the opposite of what we see on the Shroud, which therefore cannot be a conventional X-ray. So where do the X-rays of the Shroud come from? If the bones, then there should be no image of the midriff area between the ribcage and pelvis, and the ribs and collarbones should be clearly visible. And in this case, the variation in colouration of the Shroud would be due to the variation in concentration of the X-rays, and not on the alleged distance between the body and the cloth. This is not characteristic of a photographic negative.
Infra-red radiation is attenuated in air satisfactorily, and good results similar to the Shroud image have been achieved using heated bas-reliefs.
However, it should be borne in mind that the brass from which this image was obtained was of uniform material, texture and colour, while a dead, dirty, bruised, bloody body is none of those things. As such, attempts to recreate the image on the Shroud by assuming a uniform radiation from all parts of the body cannot sensibly be termed a photographic negative, or even very similar to one. If uniformity of radiation is not assumed, then the alleged relationship between intensity and body/cloth distance cannot be sustained.
The argument here is that a photographic negative is a depiction of the surface material, texture and colour of a subject, while the Shroud depicts no such thing. Its image, by contrast, is supposed to be the result of a relationship between the darkness of the discolouration and the distance between the body and the cloth. Whether that is true will be discussed in a later post.