What is image discontinuity? Pixels and 3D on the Shroud of Turin?
Images on the
Shroud emerge from discrete little bits of color in all the right places on
the cloth. The bits of color are on the fibers in a fine carbohydrate layer
that coats the topmost fibers. When we
look at the Shroud, what we perceive as different shades of yellow is the
result of
visual blending. To some extent the saturation or intensity of the color has
some effect. In some places it is slightly darker than in other places. But
mostly it the result of the size and quantity of the bits of chemically
altered carbohydrate layers on the crown of fibers. (Look at the above
picture from across the room. Only one color is used to create three
different shades.)
Pixel, a word that means picture element, is
often used to describes these tiny bits of color. The word halftone, borrowed
from the way pictures are printed in books and newspapers, is also used.
Pixel, in current usage, implies microscopic or near-microscopic dots that
are "on" or "off" and neatly organized. As the accompanying microscopic
pictures shows, the implementation of the coloring is more like lines used
for shading in an engraving. The lines are on the surface only, on fibers
that are a fraction of the width of a single hair in a fine artist's paint
brush. Paint, in any thick medium, would have resulted in a complete covering
over the fibers. Thin paint or dye of any kind would have soaked through, by
capillary action, to fibers below. But when image fibers are moved aside with
probing needles, the fibers below are clear and uncolored. And when
adhesive tape is applied to the image fibers, small bits of the carbohydrate
coating (either bearing image or not) are pulled away exposing clear cellular
fibers. In fact, flakes of color can be seen where it separated from the
fiber and stuck to tape used to collect particulate samples from the Shroud.
You can see the thin coat of color through a microscope and it is hard to
imagine how an artist could have accomplished this.
It
is important to realize that the image we are accustomed to seeing is a
negative of the image on the cloth. That is, lighter and darker
visually-blended colors are reversed. For instance the tip of the nose
contains many color bearing bits of coating close together. This produces, as
our eyes see it, a dark spot. (Incidentally, cameras, depending on the size
and granular characteristics of the film also blends the pixels). But when
reversed, the tip of the nose appears white. This phenomenon was not
discovered until 1898 when an amateur photographer, Secondo Pia, first
photographed the Shroud and saw the positive image in his glass-plate
negatives.
It is this visual characteristic of the Shroud's image that has led some to believe that the image is a form of medieval proto-photograph. Chemically, it is not so. The carbohydrate layer is not photosensitive and this is where the image resides.
When we look at the Shroud we see what looks like a picture. What to our eyes seems like the highlights, lowlights, and cast shadows of reflected light on a human form is not light at all. It is certainly not light as a camera would detect it or an artist would see it and translate it to canvas. Technical image analysis reveals no directionality to the implied light of the highlights and shadows. The brightness does not come from any angle. It is not from above or below, nor from the right or the left, nor from the front.
So what does the
visually blended tonality of the image represent if not reflected light? With
computer software we can plot the relative lighter and darker areas seen in
the images and produce a three-dimensional isometric drawing of the body.
With computerized virtual reality we can view the body from different angles.
We can see the slope of the nose, the recesses of the eye sockets and the
shape of the torso. It seems that the image is a graphic representation
of the distance between any part of the body and the cloth.
In
a sense, the images on the Shroud are terrain maps. This means that each
visually blended color shade (or the density of pixels) represents the
distance between the cloth and the part of the body the cloth is covering at
that point. To illustrate, the hazy donut shape shown here is an example of a
terrain map for the crater rendered next to it as a three-dimensional shape.
The lighter colored areas of the fuzzy donut shape represent higher altitude
in this terrain map. In the case of the Shroud, we do not get a perfect
three-dimensional rendering for many reasons. First, the distance could be
distorted by the drape of the cloth. We can assume it was not perfectly flat.
The image quenches at about 3 or 4 centimeters. That means that no image is
present for parts of the body that are more than about one and a half inches
distance from the cloth.
We don’t know how linear the scale might be in the image formation process; e.g., is twice as close twice as light. We might know the linearity if we knew how the images were created, but we don’t. Also, the image is very old—medieval or much older—and we don’t know how fading of the images and the aging of the cloth might have altered the accuracy of the distance that is encoded. Finally bloodstains and dirt certainly cause distortions.
That there is a distance encoded representation, at all, is amazing and puzzling. It is important to note that no identified works of art, artifacts or relics of any kind will produce a 3D plot like the one produced from the Shroud. Researchers have tried every imaginable artistic method including bas-relief rubbings, scorching with hot statues, daubing the surface with pigment dust, and image transfer rubbings. Nothing works to produce a 3D plot. A way to envision this is with the pic
This is startling. You cannot do this with a regular photograph or a painting or any known type of pictorial art. There is nothing at all like this imagery in the history of art.
So what does the tonality of the image—made
up of pixels—represent if not reflected light? With
computer software we can plot the relative lighter and darker areas seen in
the images and produce a three-dimensional isometric drawing of the body.
With computerized virtual reality we can view the body from different angles.
We can see the slope of the nose, the recesses of the eye sockets and the
shape of the torso. It seems that the image is a graphic representation
of the distance between any part of the body and the cloth. This is
startling. You cannot do this with a regular photograph or a painting or any
known type of pictorial art. There is nothing at all like this imagery in the
history of art.
Home Page & Introduction: The Shroud of Turin Story - A Guide to the Facts 2005
© 2004 Daniel R. Porter, Bronxville, New York
