Pam Moon was kind enough to send a paper explaining how to invert a photograph of the Shroud face on an iPhone (this is a link to the PDF of her paper). She includes some interesting information comparing “the Shroud with the detail of the painting Noli me tangere, 1304-06, by Giotto di Bondone. Giotto is arguably the most accomplished artist of the fourteenth century,” and suggesting “he clearly did not anticipate Apple technology. So, if Giotto didn’t attempt the extraordinary act of encoding a photographic negative within his work, who created the Shroud image?”

Good question.

And it’s good to add the iPhone to other graphic software. This image included with the psoting was prepared by AI. My prompt was “Hey ChatGPT, find Barrie Schwortz’s photograph of the Shroud in Pam Moon’s recent email to me and do a grayscale value inversion, ala Pia. It’s the one on the left in the PDF.”

The Shroud’s Strange Photographic Secret

When you look at the Shroud with the naked eye, the image of the man is faint and difficult to make out — just subtle, brownish discolorations on ancient linen. But something remarkable happened in 1898 when Secondo Pia took the first photograph of the Shroud and looked at his glass negative in the darkroom. Instead of the reversed, murky image he expected, he saw a clear, naturalistic face staring back at him. The cloth itself, it turned out, appeared to be a photographic negative. The recognizable image only emerges when you reverse it.

This discovery electrified the world and has never been fully explained.

What Many Found

Many researchers, including members of the Shroud of Turin Research Project, confirmed this strange property. The body image behaves like a photographic negative encoded in the cloth — mostly so, some would add. The darkest areas on the linen become the lightest when photographed, and vice versa, producing a strikingly lifelike positive image of a man.

The Blood Is Different

The reddish marks identified as bloodstains don’t follow this negative rule at all. If the cloth was wrapped around a wounded or deceased person, those marks would have transferred by direct contact — the way any bloodstain on fabric works. They appear as straightforward positive stains, not as part of whatever image-forming process produced the figure. This means the Shroud may contain two entirely different kinds of marks made by two entirely different processes.

I should add the obvious caveat: if the radiocarbon dating is correct — and I believe it probably is, give or take — then the cloth dates to the medieval period, roughly the 13th or 14th century. In that case, the “blood” would have come from whoever was wrapped in the cloth during that era, whether as a devotional object, a forgery, or something else entirely. If the image was created by an artist, we simply cannot know how the reddish marks were applied or what they represent. Science can characterize the marks; it cannot tell us the story behind them.

The Hair and Beard Problem

Ray Rogers, the lead chemist on the STURP team, noticed something that has quietly puzzled researchers ever since. The hair, mustache, and beard don’t behave the same way as the face and body image. When you invert the image photographically, the face resolves into a naturalistic positive — but the hair goes surprisingly light, appearing almost white, as if it were already behaving as a positive on the cloth rather than a negative like the surrounding skin.

Rogers had a theory. He believed those areas of the cloth may have retained more of a natural reddish substance — he suspected saponaria, a plant-based soap commonly used in the ancient world to wash linen. If more of this material concentrated in the hair and beard regions, those areas would carry a different color character from the rest of the image, explaining why they invert differently.

Let’s say for argument’s sake that the cloth really does date to the time of Christ. In that case, I think Rogers’ idea has considerably more going for it than mechanically transparent bodies, which don’t exist, or vertically collimated radiation, which doesn’t exist either. And if Rogers was right, then the idea of a modesty cloth used prior to burial — perhaps at the foot of the cross — seems more plausible to me than a full burial shroud.

Why This Matters

This distinction is subtle but significant. It suggests the image may not have been formed by a single uniform process. The body image, the bloodstains, and the hair each seem to tell a different part of the story — and no one has yet produced a fully satisfying explanation for any of it, regardless of where one stands on the cloth’s authenticity.

There is no question that the negativity is a genuine mystery. But mystery is not evidence of anything beyond the mystery itself.