I hate it when I encounter someone much smarter than me. But I love it when they do all the heavy lifting.
Hugh Farey, medievalist, Shakespearean actor and director, mathematician, scientist, and blogger has done an excellent job of challenging authenticist YouTubers who tried to rebut biblical scholar Dan McClellan’s short podcast critiques of Shroud claims made by Mel Gibson (with Joe Rogan) and popular speaker Jeremiah Johnston. Farey defends McClellan’s accuracy while dissecting the authenticists’ rhetorical failures. See: medievalshroud
Cliff Notes Version Follows
Part 1: “No Apologies” vs. McClellan on Mel Gibson
Farey analyzes a response by a team called “No Apologies” (Phill Chambers and Harvey Ward) to McClellan’s nine-minute commentary on the Mel Gibson/Joe Rogan Shroud discussion. Ward pontificates with a version of the facts he seems to have half-acquired from an “Institute of Science and Faith” course, while Chambers plays a more neutral role.
Farey structures his critique around seven methodological failures, including:
- Getting facts wrong: Ward misnames the de Charny family, misidentifies Giulio Fanti as an “Art Historian in Turin,” and refers to the Pray Codex as the “Payes painting.”
- Misrepresenting Fanti’s “personal revelation”: Ward tries to recast Fanti’s explicitly stated religious vision as merely “an emotional response to facts,” reversing what Fanti actually wrote.
- Confusing the WAXS methodology: Ward conflates the well-established WAXS technique in general with the specific and untested use of WAXS to date textiles of unknown age — exactly McClellan’s point — and then declares McClellan wrong while agreeing with him.
- Misrepresenting the d’Arcis memorandum: Ward declares McClellan’s statement about it “completely false” when he actually means he disputes d’Arcis’s credibility — which is not the same thing at all.
- Wildly misquoting Kelly Kearse: Ward claims Kearse found evidence of human blood on the Shroud; Kearse actually concluded that “cross-reactivity precludes a definitive assignment of human or even primate blood being present.”
Part 2: “Jekyll and Hyde” vs. McClellan on Jeremiah Johnston. Farey responds to McClellan’s four short podcasts critiquing Jeremiah Johnston. He nicknames the responding duo “Dr. Jekyll and Mr. Hyde” for their wild swings between calm reasonableness and unhinged abuse.
Key episodes include:
- The VP-8 Image Analyzer: Johnston falsely claims the VP-8 was “designed to study what happened to the surface of the earth after a nuclear explosion.” McClellan correctly calls this “laughably false” and uses Cicero Moraes’s simulations to argue the Shroud image looks more like a bas-relief print than a full-body print. Farey supports this, citing multiple STuRP researchers who acknowledge lateral image distortions — contradicting the authenticist claim of “perfect vertical collimation.”
- Garlaschelli’s reproduction: Hyde claims Garlaschelli himself admitted his bas-relief reproduction “sucks” and “produces nothing like the Shroud” — a claim Farey calls “a grotesque distortion.” Both Moraes and Garlaschelli, Farey notes, confirmed to him they felt misrepresented.
- The d’Arcis memorandum again: Hyde delivers a lengthy tirade claiming no credible historian accepts the memorandum, that it was never sent, and that “all the historical proof” contradicts it — assertions Farey systematically rebuts, noting that multiple documented papal bulls and other sources do describe the Shroud as a fabrication, while no document calls it genuine until a century after its first appearance.
- The retracted PLoS One paper: Jekyll first agrees with credible pro-Shroud experts that the Carlino et al. paper on “biologic nanoparticles” was unreliable, then Hyde insists it was never retracted, basing this on an interview with a disgruntled author.
- Neutron irradiation and radiocarbon dating: Hyde claims Thomas McAvoy’s Applied Optics papers prove a “precise match” between UV fluorescence and neutron irradiation calculations. Farey states flatly that neither McAvoy paper even mentions neutron radiation, and that in his own extended correspondence with McAvoy, no such correlation actually exists.
Overall Thesis
Taken together, Farey’s two posts make a pointed argument: the authenticist counter-response to McClellan is not only factually weak but actively self-defeating. This kind of thing, he writes, “discredits authenticity even more thoroughly than the actual research that I and like-minded medievalists publish ourselves.”
Refuting Jeremiah Johnstons claims is not equal refuting the authenticity of the Shroud.
Otangelo Grasso wrote: “Refuting Jeremiah Johnston’s claims is not equal to refuting the authenticity of the Shroud.”
I agree entirely. Farey is right to be critical of Johnston — such sloppiness genuinely hurts the overall search for truth, regardless of which side of the authenticity question one lands on. Sloppy advocacy is worse than no advocacy.
But let’s think through what we’d actually have, even in the most favorable scenario for authenticity.
Say for argument’s sake that the published C14 results are wrong and the cloth really does date to the time of Christ. And say further that we can establish with a high degree of certainty — supported by historiographic evidence — that the image depicts Jesus of Nazareth following his crucifixion. Grant all of that.
What do we actually have?
It might be his burial shroud. Or it might be a pre-burial covering used during the preparation of the body. Or — and this is a possibility that rarely gets serious attention — it might be a work of art produced by some method we have not yet been able to imagine, created by someone who knew Jesus, witnessed the crucifixion, or had access to detailed accounts of it. The first-century world was not without gifted craftsmen, and our failure to reproduce a technique does not prove the technique is miraculous or supernatural.
In other words, even a best-case authentication of the cloth and the image leaves the deepest theological claims unproven. The leap from “this is a first-century linen bearing the image of a crucified man matching Jesus of Nazareth” to “this image was produced by the Resurrection” is not a scientific inference — it is a faith commitment. That doesn’t make it wrong. But it does mean that the Shroud, at best, can be consistent with faith. It cannot be the foundation of it.
Which is perhaps why the most honest position is the one Farey implicitly models: rigorous about the evidence, humble about the conclusions.
” it might be a work of art produced by some method we have not yet been able to imagine, created by someone who knew Jesus, witnessed the crucifixion, or had access to detailed accounts of it. ”
I think that hypothesis can be excluded with reasonable doubt, in the face of the fact that even today, we cannot replicate the image.
When we consider the 25 constraints for the image formation alone, leaving all the other hurdles aside, the picture becomes pretty clear:
The Shroud of Turin: A Unified 25-Constraint Scientific Framework for Image-Formation Mechanism Evaluation
https://www.academia.edu/143734765/The_Shroud_of_Turin_A_Unified_25_Constraint_Scientific_Framework_for_Image_Formation_Mechanism_Evaluation
and here an overall assessment of the evidence for the Shrouds authenticity:
https://www.academia.edu/142994424/Evidence_Supporting_the_Shroud_of_Turins_Authenticity_A_Comprehensive_Scientific_Analysis
And the most comprehensive aproach is in my recently published book, available on Amazon: The Shroud of Turin: A Forensic Summary of the Evidence
https://www.amazon.com/Shroud-Turin-Forensic-Summary-Evidence/dp/B0GRTXM6GV/ref=sr_1_2?crid=ONDNAADGTKQ5&dib=eyJ2IjoiMSJ9.cTwAFwujYdVkwYfxbGggv0dKcjmEGv3PMYl2au-U-ERW83BB6LFWn5q-aiAboOO9kTmt29hs8sP2Z1059AdtIA4R4nHSPG9c46CHg5c26YMvzhs0N7csyQsconeRpQkhu0_SZU7fe6ag_wYj1AuXwxh84_OJg_gPm85sBWslXlS9JSHT0HMdHw81rjehqORvyKd-_gVsCJA34oHmD-gScKFnZHcWI1GsxD__BmxdqGo.l5Zqii1xdbqKLlfOOjmF7NO3o-La-XrH0Kz_prPZcdQ&dib_tag=se&keywords=otangelo+grasso&qid=1776531324&s=books&sprefix=ota%2Cstripbooks-intl-ship%2C1512&sr=1-2
Hi Dan,
That’s a very kind assessment of my homework, so thank you very much. I particularly like the last eight words, and hope that you won’t mind if I adopt them as a byline.
Best wishes,
Hugh
In effect this is not an actual pro-Medievalist argument as much as a form of ad hominem/poisoning the well fallacy to imply if they get these facts wrong then you cannot believe anything they say. But the facts themselves remain unaddressed. One clear case of obfuscation is conflating the misstatement of why the VP-8 3D image analyzer was invented and then pulling a complete bait-and-switch to discussing Cicero Moraes’ work that not only has nothing at all to do with the 3D information in the Shroud but is ITSELF disqualified BECAUSE the bas-relief method he proposed cannot produce 3D embedded information in the first place (and relies on pigments, dyes or paint which were not used as well). This is highly deceptive. Point out one inaccurate piece of data that actually has nothing to do with the fact that the image actually has embedded 3D information, and then switch to a complete red herring about a study that itself has nothing to do with 3D information and couldn’t produce it in the first place. Leaving the fact that the image HAS 3D embedded information conveniently ignored and intentionally lost in the switch. Nearly all of these points do the same rhetorical trickery: Raise one factual misstatement and then switch to a red herring to address something actually unrelated to side step and cause people to skip over actually addressing the facts. Another example: This is done with the neutron flux hypothesis that both explains the added C14 (and thus younger date overall), as well as the way the C14 age got younger the closer to the body the samples were taken, and two other independent lines of evidence including the UV Fluorescence observed distribution and observed changes to blood chemistry and detected radioactivity of the blood itself. None of these facts were actually addressed. Instead a mistaken attribution to a different author’s papers was used to imply none of these are true when papers published by Bob Rucker provide clear and detailed analyses that prove all of these points. Especially the clear evidence from the original C14 studies of contamination shown by the fact the age decreased by 36 years/cm and the dates being outside the error bars for this dating technique.
Hi Robert,
Good to hear from you. It was not my intention in my last two blog posts to assess any facts as such – I do that extensively elsewhere – but to notice that, contrary to your optimistic assertion, if people get lots of their facts wrong – and if you know they’re wrong, and culpably so – then you really cannot believe anything they say without verifying it yourself.
But even that’s not really the point. As few of Jeremiah Johnson’s interviewers seem to know anything about the Shroud, they don’t know that he’s got his facts wrong, and so they do believe everything he says, true or false. And thus a large consensus, based on falsehood, is created, which anybody serious enough to check soon discovers, to the detriment of the cause of those who base their authenticism belief on real facts rather than fantasy. Jack Markwardt expressed this rather well in his key-note address to the St Louis conference recently.
Ironically, while McClellan’s, and my, comments were certainly not a bait-and-switch, your comments above certainly are. The VP8 image looks like a bas relief, and a print from a bas relief can produce a VP8 image very similar. This has been shown repeatedly. Your confidence that it can’t is misplaced. It is you who then introduce the irrelevance – to this argument – about the putative method by which the print was made.
The point is not that the Shroud has or hasn’t got 3D information embedded in it – nobody denies that – the point is that the 3D information, at least as interpreted by the VP8, unfolds into a representation of a bas relief, not of a real human body. This is largely ignored by authenticists, who insist that it looks like something it doesn’t.
Your next point is not wholly clear to me. You say “raise one factual misstatement…” but I’m not sure what you’re referring to. I try very hard not to say anything factually inaccurate, so if you point it out I’ll be glad to correct it. You also mention a “mistaken attribution to a different author’s papers,” which I don’t follow. What was the “mistaken attribution”? And finally, you mention papers by Bob Rucker that “provide clear and detailed analyses that prove all of these points.” The points seem to be connected to Tom McAvoy’s hypothesis about fluorescence and Giulio Fanti’s hypothesis that the blood is radioactive, but I can’t find any mention of these among Bob’s papers. Can you say which they are?
Best wishes,
Hugh
Hi, Everybody,
David Johnson of “Skeptics and Seekers” referred to me (after the second time that I was a guest on his podcast and a frequent commenter in the comment section to the various shows that he would put on) as a “Shroud First Christian.” He’s right.
The Shroud doesn’t just stand alone in a vacuum–it needs both secular and non-secular historical evidence to give it Its greatest weight, force and understanding, but it is the singular most important piece of evidence that we have that the God of Christianity if real. I stand by that statement with every fiber of my being, and I put my credibility on the line regarding this reason and evidence-based belief of mine that I believe is so strong that reasonable doubt cannot be had regarding Its authenticity. Again, I stand by that with the fullest of force. No single piece of evidence will ever be 100% perfect for anything–except our knowing that we are conscious by way of our ability to think. But, with the body of evidence for the Holy Shroud’s authenticity being so strong–and with the context surrounding that evidence telling us WHAT the Holy Shroud is and WHEN Its images were produced, I really do not think that reasonable minds can disagree on that. I just really don’t–not if you take all of the evidence into consideration and merge it with Reason and Context. It’s a done deal–and that’s a GLORIOUS, GLORIOUS, GLORIOUS thing to be able to say with the purest of heart, the purest of mind and the force of the Holy Spirit behind that statement. I stand by this and will not waiver on it.
For a layout of the context for the Holy Shroud’s being evidence of Jesus’ resurrection, please listen to my speech at the St. Louis conference from 2025. https://youtu.be/HK1DPmxa6G0?si=at66EVb4-vvIzh6L
All the best,
Teddi
Also, I will add that one can certainly have excellent reasons for being a full-throated Christian without believing that the Holy Shroud is authentic. But, one’s ability to defend the Truth of Christianity to its fullest force will be hampered as clever atheists poke holes here and there in the reliability of what the Holy Bible states. The Holy Shroud just knocks to smithereens the doubts that these atheists try to sow about the reliability of the Holy Bible’s message about the Christian God. I was a Christian prior to learning about the Holy Shroud at around age 15. But, admittedly, my belief in Christianity at that age was based on what I had learned from my family and Sunday School and Bible classes offered at both a Lutheran school that I went to for three years and a Baptist school that I went to for two years. Back then, I had not heard the clever arguments that atheists make. Now, having heard them, and even without the Holy Shroud as evidence, I would still be a Christian, but my level of confidence would not be anywhere near as high as it is with the Holy Shroud evidence. Particularly in times of crisis, it is a wonderful gift that God gives us to be able to have not perfect evidence, but evidence beyond a reasonable doubt that He is real. What a gift to those who are receptive to receiving it and who will bend their knee to God.
And, just like Detective Columbo, “just one more thing . . .” Regarding people who appear on shows or conferences or put on exhibits regarding the Holy Shroud, it is important for everyone to know that the sheer volume of information concerning the Holy Shroud is beyond encyclopedic. No one person can perfectly defend the ins-and-outs of every piece of evidence. It’s just too much. So, instead, people focus on evidentiary highlights. However, many of these presenters have just, perhaps, read some Shroud papers but rely mostly on other peoples’ bulletpoints of the highlights. So, old information often gets repeated without these people being aware that it is old. And, a serious problem is that some Shroud presenters will know that certain evidence is no longer warranted, but because they have already been on the record for too long making certain claims (like the supposed AB blood type and species of the blood, etc.) they are resistant to updating their information–probably from not wanting their supposed “expert” status to be undermined (particularly since they did not “correct course” early on when it was discovered that this evidence was no longer viable.) So, that is a problem–a very, very serious one, and it is dishonest.
The Dunning-Kruger effect is real–and it is evident among many people who present Holy Shroud evidence to the public. Many of these people are just so excited to share what they know about the Holy Shroud–and that’s understandable–but they have not studied the evidence deeply enough (in terms of the various arguments, counter-arguments, etc.) to know what they don’t know. So, they think they know what they need to know–but, the really don’t. Most of the time, the highlights that they know are the tip of the iceberg, and they cannot discuss matters on a deeper level. And, often, their audience isn’t interested in a deep dive on matters that can be difficult to understand if one is not well-versed in Science. But, the failures of these presenters do not undermine the validity of the reliable data gotten from the STURP team, in particular. The best thing for people to do is to read the original papers by, especially, Heller and Adler and Adler’s “The Orphaned Manuscript” which is available for free on Shroud.com under their Shroud Spectrum International pieces. Heller’s book, “Report on the Shroud of Turin” is required reading for anyone who is serious about learning about the investigation that STURP performed on the Holy Shroud in 1978.
People need to go to the PRIMARY SOURCES for their information, and just let the popularizers concerning the Holy Shroud whet your appetite to learn more about it. The popularizers mean well, but they often do not get all of their evidence right. People should rely on the evidence that they get from the proverbial horse’s mouth.
Hi Robert. I think it’s important to be careful about how we’re using the term ad hominem. Not every critique of an author’s reliability falls into that category.
An ad hominem fallacy, strictly speaking, is when someone dismisses a claim solely because of who made it—for example, “he’s from Kentucky, therefore he’s wrong.” That would be irrelevant to the truth of the argument.
What’s happening here is different. If an author demonstrably misstates key facts—especially in areas central to the argument—that legitimately raises questions about their reliability on closely related claims. That’s not “poisoning the well”; it’s evaluating the credibility of the source based on performance. In any serious field, repeated or significant errors do weaken confidence in the conclusions drawn.
That said, I agree with part of your concern: credibility critique shouldn’t replace engagement with the actual claims. The strongest approach is both—(1) identifying errors where they exist and (2) directly addressing the underlying arguments.
On the 3D issue specifically, the point being made is not that “there is no 3D information,” but that the so-called 3D effect (e.g., from VP-8 analysis) does not uniquely imply a physically 3D-encoded image in the way often suggested. Many non-Shroud images and relief mappings can produce similar intensity-to-distance correlations under certain conditions. So the existence of a VP-8 response, by itself, is not decisive evidence for any particular image-formation mechanism.
Likewise, with hypotheses like neutron flux or radiation-based explanations: these are not being ignored so much as regarded as highly speculative, because they require multiple independent assumptions (radiation levels, spatial gradients, interaction with linen and blood chemistry, etc.) that are not directly evidenced and would need to be demonstrated, not just asserted as explanatory.
So I’d frame it this way: pointing out factual errors is not inherently ad hominem—it becomes fallacious only if it substitutes for engaging the argument. The real question is whether both are being done.
” the so-called 3D effect (e.g., from VP-8 analysis) does not uniquely imply a physically 3D-encoded image in the way often suggested. ”
The VP-8 was never the star of the show
The VP-8 Image Analyzer is a nifty piece of 1970s NASA‑derived tech. It turns shades of gray into a topographical map: dark becomes high, light becomes low. When you feed it an ordinary photo, you get a meaningless jumble of bumps and dips. But when John Jackson and Eric Jumper fed it a photograph of the Shroud in 1976, out popped a perfect human face—anatomically correct, with the nose high, eye sockets low, cheeks rounded.
Peter Schumacher, the engineer who invented the VP-8, said he’d never seen anything like it before or since.
So why isn’t that proof? Because the VP-8 is indeed imperfect. Any image with smooth, gradual shading can produce a vaguely face‑like relief. The device assumes brightness = height, which isn’t physically true. A clever artist might, in theory, paint a “3D‑looking” picture that fools the VP-8.
But the VP-8 was only a visual aid. The real evidence came from a much more boring instrument: the microdensitometer.
The real evidence: microdensitometry
A microdensitometer measures the exact darkness of an image point by point. Jackson and Jumper used one to scan the Shroud photograph. Then they independently calculated the distance between the cloth and an imagined human body underneath—based on the geometry of a draped linen sheet over a standing or lying figure.
What they found was a clean, mathematical relationship: the darker the image, the closer the cloth was to the body. The tip of the nose is dark because the cloth touched it. The eye sockets are faint because the cloth bridged over them. This wasn’t a rough correlation—it was precise and consistent across the entire cloth.
That’s not a visual illusion. That’s data.
What does this rule out?
Let’s list the ways you could normally put an image on cloth:
Painting – An artist paints where they want color, not where the cloth is closer or farther. Plus, STURP found zero pigments, binders, or brush strokes.
Rubbing or pressure – Press a cloth against a face, and it gets dark where you push hardest, not where the cloth is closest. The Shroud’s nose is dark on the sides, not just the tip—pressure would do the opposite.
Liquid or vapor diffusion – A chemical fuming from the body would create fuzzy halos and would follow the weave of the cloth. The Shroud’s image ignores the weave entirely.
Photography – A camera records reflected light, not distance. The Shroud has no perspective distortion—it’s not a photograph.
Isotropic radiation – If the body emitted light or heat equally in all directions, the cloth would get an image on the sides too. The Shroud has only front and back.
The only mechanism that can produce a distance‑encoded image is directional radiation—some kind of beam or field that travels in straight lines from the body to the cloth, fading with distance. Think of a collimated light source, or a corona discharge, or a directed particle flux.
The odds: let’s do the math
Now for the question you came for: what are the chances that a randomly chosen image‑forming process would accidentally produce this 3D encoding?
We can estimate by counting mechanism classes.
Crude method (6 broad classes):
Painting
Contact transfer
Diffusion
Photography
Isotropic radiation
Directional radiation
Only one class (directional radiation) works. If all classes are equally likely, the probability is
1
6
≈
16.7
%
6
1
≈16.7%. But that’s too generous—within “painting” there are dozens of techniques, all of which fail. So we need to count sub‑mechanisms.
Refined method (sub‑mechanisms):
Painting variants: ~10
Contact methods: ~5
Diffusion processes: ~8
Photographic methods: ~4
Isotropic radiation types: ~3
Directional radiation types: ~2
Total conceivable mechanisms: ~32. Working mechanisms: 2 (directional radiation, plus maybe an exotic standing wave).
That gives
2
32
=
0.0625
32
2
=0.0625, or about 1 in 16.
The peer‑reviewed estimate from the source document you’re referencing combines the 3D constraint with another independent constraint (fold independence) to get
P
=
0.05
P=0.05, or 1 in 20.
So, roughly: only 5% of physically possible image‑forming processes could produce the Shroud’s distance encoding.
What does 1 in 20 mean in plain English?
If you started with a completely open mind—50% chance authentic, 50% chance forgery—then the 3D evidence alone would shift your odds to 20:1 in favor of authenticity. That’s strong, but not airtight. (You’d need a few more independent constraints to reach 99.9% confidence.)
But here’s the kicker: that 1 in 20 counts all conceivable mechanisms, including futuristic ones like lasers or particle beams. When you restrict the question to techniques available in the Middle Ages, the number of working mechanisms drops to zero. No medieval artist, no matter how clever, could have painted or rubbed or fumed a global distance map onto linen without leaving pigments, pressure marks, or weave patterns.
That’s why the STURP team—32 scientists, many skeptical—concluded in 1981: “The image remains scientifically unexplained.”
But what about the 2025 Moraes study?
You may have heard that Cicero Moraes recently argued the 3D effect could come from a low‑relief sculpture, not a real body. That’s a legitimate challenge, and it’s worth taking seriously.
However, Moraes’s work is a digital simulation, not a physical replication. It does not reproduce the microdensitometric distance correlation—only the VP‑8’s visual appearance. And it still suffers from the contact‑pressure problem: a cloth pressed against a bas‑relief gets darker where pressure is highest, not where distance is smallest. Those are different things.
So the 2025 study is an interesting hypothesis, but it hasn’t overturned the original 3D encoding evidence. It has only shown that the VP‑8 alone isn’t proof—which we already knew.
The bottom line
The VP‑8 is imperfect, and its output alone does not uniquely prove a 3D‑encoded image. That criticism is valid.
But the VP‑8 was just a pretty picture of the real data: microdensitometry showing a clean
1
/
d
1/d relationship between image darkness and cloth‑to‑body distance.
That relationship rules out all known artistic techniques from the Middle Ages.
The odds that a randomly chosen mechanism would produce it are about 1 in 20 (conservative estimate) or effectively zero if we only consider medieval methods.
So yes, the statement “the so‑called 3D effect does not uniquely imply a physically 3D‑encoded image” is correct—if you’re talking only about the VP‑8. But the full body of evidence, including the microdensitometer, pushes us right back toward that conclusion anyway.
The Shroud remains a scientific riddle. And the 3D encoding constraint is a big reason why.
Hi Otangelo. I think there’s an important distinction being blurred here regarding what the microdensitometer actually shows.
A microdensitometer measures optical density—how dark or light each point of an image is. It does not measure distance, height, or cloth-to-body separation. So when it’s said that Jackson and Jumper “calculated distance from the data,” that step is already model-dependent. It requires assuming a specific relationship between image intensity and distance (for example, something like an inverse or exponential decay). That relationship is not directly observed—it’s imposed.
And that’s the key issue. A smooth, monotonic gradient in intensity can be made to fit a “distance-like” curve under a variety of assumptions. But smooth gradients are extremely common. A simple example: place a drop of ink or food coloring on a porous surface and let it diffuse outward. You’ll get a dark center fading to lighter edges. Scan that with a microdensitometer and you’ll obtain a clean intensity gradient. You could then fit that to a distance model—but there is no underlying 3D geometry at all. It’s just diffusion.
So the presence of a correlation between darkness and a modeled “distance” does not demonstrate that the image encodes actual spatial information. It demonstrates that the image has coherent tonal variation—which many processes can produce.
That’s why statements like “this rules out painting, contact, diffusion, etc.” are too strong. Those mechanisms can also generate smooth gradients, depending on conditions. The conclusion that only “directional radiation” can account for the data depends heavily on prior assumptions about how the image must have formed.
The same applies to the probability argument (“1 in 20”). That figure is based on arbitrarily grouping and counting mechanisms, not on a defined statistical framework. It gives the appearance of rigor without a real basis.
So yes, the VP-8 alone doesn’t prove anything—we agree on that. But the microdensitometer doesn’t independently establish “distance encoding” either. It provides intensity data. The interpretation of that data as cloth-to-body distance is a hypothesis, not a direct measurement, and alternative explanations remain very much on the table.
You are correct to distinguish between measurement and interpretation. Let me respond directly and point-for-point.
1. You are right: the microdensitometer measures optical density, not distance
Absolutely correct. A microdensitometer returns a number—how much light passes through or reflects off a point on the image. That number is intensity, not meters or centimeters. The claim that the Shroud encodes cloth-to-body distance is not a raw measurement; it is an inference based on correlating intensity data with a geometric model of a draped cloth over a human form.
So the objection stands: the step from “dark here, light there” to “cloth was close here, far there” requires assuming a specific relationship (e.g., inverse or exponential decay). That assumption is not directly observed.
However, this is not a weakness unique to Shroud research. It is how all indirect measurement works. In science, we often measure one thing (intensity) and infer another (distance) by testing a model. The strength of the inference depends on:
How well the model fits the data across independent points
Whether alternative models (other relationships) fit better or worse
Whether the inferred distance map makes anatomical sense
Jackson and Jumper did not simply say “dark = close.” They took a separate, independent calculation of cloth-to-body distance based on draping a linen sheet over a human-shaped form (using known geometry of the Shroud’s dimensions and the proportions of a male body). Then they plotted measured intensity against that calculated distance at dozens of points. They found a clean, monotonic relationship. That relationship was not assumed—it was discovered.
2. The diffusion counterexample: a drop of ink
You give an excellent example: a drop of ink on a porous surface produces a smooth gradient. A microdensitometer would measure a dark center fading to light edges. You could then fit that to a distance model and claim “3D encoding”—but there is no 3D geometry. It’s just diffusion.
This is a legitimate caution. But the Shroud case differs in three crucial ways:
First, the gradient is not radial. A drop of ink produces a circular or elliptical gradient centered on the point of application. The Shroud’s gradient follows the contours of a human face—the nose is dark, the cheeks are medium, the eye sockets are light, and these features are in anatomically correct positions. A diffusion process does not spontaneously arrange a face-shaped gradient unless the source itself is face-shaped. But if the source is a face, then we are back to some form of contact or emission from a 3D form.
Second, the gradient ignores the cloth’s weave. Diffusion through a woven fabric is strongly affected by capillary action along threads. The Shroud’s image shows no preferential darkening along warp or weft lines. That is highly unusual for any liquid or vapor diffusion process. STURP examined this and found the image sits on top of the fibers (only the outermost 1-2 fiber diameters) and does not wick into the thread interiors.
Third, the gradient persists across non-contact regions. In a diffusion gradient from a face, areas where the cloth is farther away would receive less diffusing agent—but the relationship is not simple inverse distance because diffusion in air is 3D and the cloth is a 2D sampling surface. The observed fit to a 1/d or exponential curve is remarkably tight. Could diffusion produce that? Possibly, but no one has replicated it using medieval materials and methods.
So the ink-drop analogy is useful as a warning, but it does not explain the Shroud’s specific pattern.
3. Does the correlation rule out painting, contact, and diffusion?
Your objection says those mechanisms “can also generate smooth gradients, depending on conditions.” That is true in principle. A skilled painter can create a smooth gradient. A rubbing can produce a soft edge. Diffusion can produce a fade.
But the Shroud’s gradient is not merely smooth. It is globally monotonic with a specific geometric model (cloth-to-body distance) and independent of local contact pressure, weave, and folding. Those additional constraints are what rule out the alternatives.
Painting: An artist could paint a smooth gradient, but STURP found no pigments, binders, or brush strokes at the microscopic level. Moreover, an artist would have to calculate the distance map in advance—a 3D engineering task with no precedent in medieval art.
Contact: Pressure darkens where force is highest. On the Shroud, the nose bridge is dark, but the tip of the nose is not darkest. Pressure would make the tip darkest. Also, the image appears where the cloth did not touch the body (eye sockets)—contact cannot explain that.
Diffusion: Diffusion gradients follow the weave and create halos. The Shroud’s image ignores the weave and has sharp boundaries (e.g., between the nose and the background). No diffusion model has reproduced the Shroud’s pattern.
So “smooth gradient” is necessary but not sufficient. The Shroud’s gradient has specific properties that narrow the field dramatically.
4. The probability argument (“1 in 20”) is heuristic, not rigorous
You are correct here as well. The 1-in-20 figure is not derived from a formal statistical model with defined sample spaces and frequency data. It is a subjective Bayesian prior—an expert elicitation based on enumerating conceivable mechanism classes. It gives the appearance of precision without true statistical foundation.
I should have been clearer about that. The proper way to present it is:
*”Given the constraints (no pigments, no pressure marks, weave independence, non-contact regions), only a narrow class of directional attenuation mechanisms appears physically possible. Among the many conceivable image-forming processes, a reasonable subjective estimate places the probability that a randomly selected mechanism would satisfy all constraints at around 5% or less.”*
That is a statement of informed judgment, not a mathematical proof. And reasonable people can disagree on the prior.
However, even if you reject the 1-in-20 number entirely, the core observation remains: no one has produced a medieval-compatible technique that replicates the full set of Shroud image properties. That is an empirical fact, not a probability.
5. The core unresolved issue
Your objection’s strongest point is this:
“The interpretation of [microdensitometer] data as cloth-to-body distance is a hypothesis, not a direct measurement, and alternative explanations remain very much on the table.”
That is fair. The distance-encoding interpretation is indeed a hypothesis—but it is a hypothesis that has survived decades of testing, has been replicated by multiple independent researchers, and has not been falsified by any proposed alternative mechanism that actually works with medieval materials.
Alternative explanations are “on the table” only in the sense that they have been proposed. None have been demonstrated. A low-relief sculpture (Moraes 2025) is a hypothesis, but it has not been physically replicated, it suffers from the pressure problem, and it does not explain the weave independence or the lack of pigments.
So the correct scientific stance is:
The Shroud’s image has a measurable intensity gradient.
That gradient correlates well with a model of cloth-to-body distance.
This correlation is consistent with, but does not prove, that the image formed by a directional distance-attenuating mechanism while draped over a real body.
Alternative explanations have been proposed but not successfully demonstrated.
Therefore, the 3D encoding constraint is a strong clue but not an ironclad proof.
Conclusion to the objection
You have raised valid points. The microdensitometer does not directly measure distance. The “1 in 20” odds are heuristic, not rigorous. Diffusion and other processes can produce smooth gradients. And the distance-encoding interpretation is indeed model-dependent.
Where I would push back gently is on the implication that this reduces the Shroud to just another smooth gradient. The specific pattern—anatomically correct, weave-independent, pressure-independent, non-contact encoding—is not explained by any known pre-modern technique. That remains true.
So the statement you originally quoted—*”the so-called 3D effect does not uniquely imply a physically 3D-encoded image”*—is still correct. But the stronger claim that the image actually does encode distance information remains a well-supported hypothesis, even if not uniquely proven.
Thank you for the push. It made the argument sharper.