[d_theorist]

Of course they weren’t dumb, but having a great understanding of shadows is a far cry from being capable of creating a photo negative. They didn’t even have the concept of a photo negative. How would they even have thought to achieve such a thing? And for what purpose?

And, by the way, the image on the shroud is not made of paint, so contemporary proficiency with painting techniques hardly seems relevant.

[codingdave]

Why would they need the specific concept of a photo negative? A negative is just a reversal of light/dark. They knew of such things. They knew primary colors, too. Painting and mixing colors is not exactly modern -- it has been around for many centuries. Artists practice playing with light and color as basic exercises, and have done so for hundreds if not thousands of years. Switching light and dark is a fairly basic concept to artists, not an innovation that required photography to exist in order to conceptualize it.

In the same vein, why would it have to be made of paint? Paint is simply pigment inside a medium. Dyes are also pigment, in different medium, made to soak into and bind with cloth instead of being layered on top.

I'm not saying that is how it was created, but I highly doubt that the skills to do so did not exist.

[svieira]

It was not dyed - the fibers that are discolored are discolored only on one side.

[d_theorist]

Why would they have done it?

[thordenmark]

They did not know primary colors. They weren't discovered until the 19th century, even then it took another 100 years before they figured out that red blue and yellow are not the primaries.

[Tagbert]

They were very familiar with rubbings where you place paper or canvas on a sculpture or incised surface and rub charcoal on it to capture the image. The result is very much like a negative.

[nonameiguess]

A negative is just an inversion of the intensity of visible signal. It even has a manifestation in common experience. Stare at something for a long time, then look away. A negative will superimpose on whatever you're now looking at it. I can't think of a good reason humans of the past should not have been able to reproduce this kind of effect artistically.

[InsideOutSanta]

"being capable of creating a photo negative"

You're calling it a photo negative. It's not a photo negative. It's a painting that has shadows and lights inverted.

"the image on the shroud is not made of paint"

It's made of red paint.

[Fidelix]

Not true at all. No red paint in it.

This has been conclusively, scientifically debunked multiple times.

[svieira]

Red paint that isn't visible under an electron microscope is some pretty advanced paint.

[tristramb]

It could be survivorship bias. All the fake shrouds with botched images were recognised as fakes and thrown out long ago. Only this one which happens to look vaguely realistic has been kept.

[briffid]

Plus what must have been lost in 500 years, all photonegative pictures, fragments, descriptions, recipes, any references for such imagery etc. It is very strange that this is the only image that remained. And an image of a nude Jesus from the back. For which no other instance is known anywhere.

[ithkuil]

Xylography (woodcut) technique also uses negatives. The technique is ancient in China and it has been attested in 13th century Europe

[gqcwwjtg]

A photo negative in a single color is not a tough concept to stumble upon if you ever carve something to be thin enough to let light through.