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The Shroud and Modern Science
For centuries the Shroud of Turin was revered for the light sepia colored, and hard to discern, image of a man bearing wounds many believers held to be consistent with the trauma wounds of scourging and crucifixion. In limited circles some even came to venerate the cloth as being the burial cloth of Jesus of Nazareth. Then, in 1898 things took a dramatic turn. While the Shroud was being exhibited in Turin, an amateur photographer by the name of Secunda Pia was invited to take the first photographs of the Shroud. On the evening of May 28, 1898 during the normal course of developing his photographic plates, Pia was startled to see the unmistakable image of a crucified man that was nothing like the image seen by the naked eye when looking at the Shroud. The image he saw looked very much like a true photographic positive. The image on the Shroud itself must then logically be the photographic-like negative. This discovery was propagated around the world. Wide spread popular interest in the Shroud was kindled and for the first time scientific eyebrows were raised. Modern scientific interest in the Shroud can be said to have began with Pia’s photographs and that interest has continued to grow to the present day. Figure 1 shows what Pia’s negative of the face on the Shroud revealed to the world.
Figure 1: Pia Negative
The scientific significance of Pia’s discovery is twofold. First, the shading of the Shroud body image is like a negative, where shades of light and dark are reversed from the way they normally appear in ordinary visual experience. That is, we are used to seeing people with light highlights and dark shadows. But on the Shroud, this shading convention is reversed. The immediate question that arises from this result is how could the Shroud sensibly be the work of an artist or craftsman? Such a person working in the Middle Ages around the year 1357, when the Shroud first surfaced in Europe in the tiny village of Lirey France, would have to have worked with an absolutely unfamiliar and unnatural shading structure before the advent of photography. If the Shroud is older, then the dilemma simply becomes more perplexing. The second significant aspect of Pia’s discovery is that the information density, or correlation with anatomical subtleties of a human body, is exceedingly high, well surpassing that expected of artistic renditions of the human form by even the great masters. In the negative, the image indeed appears to have the quality and detail of a photograph.
In 1902, the French Chemist Paul Vignon, in studying Pia’s photograph , thought that the intensity of the Shroud image seemed to vary with expected cloth-body distance. That is, the closer the draping Shroud was to a presumed underlying body, the more intense was the body image. While he could not demonstrate this observation quantitatively at that time, he nevertheless proposed that the image was due to ammonia vapors emanating from the body surface as an attempt to explain the distance correlation.
In 1931, the Shroud was again photographed, this time by Giusseppi Enrie, another Italian photographer. These photographs again showed the negative characteristics of the Shroud image, but with even more fidelity. The positive and negative image of the Enrie photograph of the face are shown in Figure 2.
Note blood stains are dark to naked eye but light on the negative.
In 1974, it became technically possible to rigorously test Vignon’s intensity versus cloth-body hypothesis. Using a microdensitometer, an instrument that measures intensity of a photograph, and a reconstruction of how a cloth model of the Shroud drapes over a body, American Physicist John Jackson and colleagues were able to show that, indeed, image intensity does vary with cloth-body distance with a high degree of correlation. It occurred to Jackson and his team that this correlation might be empirically demonstrated using a special image analysis technique. The thought was to plot image intensity as corresponding levels of three-dimensional topographical relief. The hypothesis was that if the intensities of the Shroud image do indeed correlate with cloth-to-body distance, then the resulting relief image should correspond to a sensible three-dimensional form of a human body, excluding any second order effect of cloth drape.
Early in 1976 the opportunity to empirically test the team’s hypothesis presented itself. On February 19, 1976, Jackson brought a photograph of the Shroud to the image analysis laboratory of Sandia National Laboratory’s Bill Mottern, The Shroud image was studied using an analogue computer called a VP-8 Image Analyzer that was able to directly convert image intensity to vertical relief. Astonishingly, the relief image was anatomically correct for a human body, even down to the subtle details of the face. Figure 3 shows the software VP-8 emulator relief of the face image based on the Enrie negative, Figure 2 from which it was derived.
Figure 3: Enhanced VP-8 Emulator Relief of Face
It became very important to note how the intensities of various image features in the Enrie photograph, especially those of the face, hands and chest, have been interpreted by the VP-8 as corresponding levels of relief. These details and their fidelity to realism became, and remain, important benchmarks in any effort to evaluate competing hypotheses concerning the mechanics of image formation. We will speak further to this in the next topic on Image Characteristics. For now, simply note that the 3-D structure of the VP-8 image of the face shown in Figure 3 resembles to a high degree of fidelity a realistic human form. Look again carefully at the facial relief image.You can see, to within the resolution capabilities of the VP-8 system used in 1976, that the entire three-dimensional facial structure of a normal human face is reproduced accurately. Note that the nose is higher in elevation than the cheeks, which are both higher than the eye socket. Further note that the relief structure of the lips is in proper three-dimensional relation to the nose and cheeks. If you compare with Enrie’s facial image, you can see precisely why the VP-8 relief has these characteristics. The nose is plotted with the highest relief because it has the brightest intensity. The cheeks are less bright and, consequently, they wind up with correspondingly less topographical relief than the nose. It is of important empirical significance that the VP-8 relief was generated from a SINGLE function of relief versus intensity. This fact leads directly to the remarkable empirical conclusion that the 3-D intensity correlation must be a fundamental characteristic of the Shroud image itself. Use of more modern equipment simply confirms the conclusion reached with the VP-8 equipment back in 1976.
Proceed to our next topic for more specifics on the Shroud Image.
Figure 2: Enrie Naked Eye Shroud on left, Negative on right.
