Read Stephen Jones’ posting on his blog and study the graphics. Stephen may be right but I need to look into this a bit more. I was trying to replicate Ian Wilson’s folding pattern. I’m not convinced that tetradiplon is four doublings in the most literal sense or doublings into what is essentially fourths. Give me your comments. And allow me some time to consult with others. Here is a bit of what Stephen has to say:
A commenter on Dan Porter’s Shroud of Turin blog pointed out what I had previously realised, but had forgotten, that Dan’s "Tetradiplon" graphic illustrating how the Shroud of Turin, when "four-doubled" (Greek tetradiplon), with Jesus’ face uppermost, results in Jesus’ face only within a rectangle, in landscape aspect (exactly as in the oldest copies of the Image of Edessa), has a flaw in that it only shows three doublings of the Shroud (see above).
Even Ian Wilson’s illustrations of this in his books (e.g. "The Evidence of the Shroud," 1986, p.113; "Holy Faces, Secret Places," 1991, p.142; "The Blood and the Shroud," 1998, p.153; "The Turin Shroud," 2000, p.111; and "The Shroud," 2010, p.141), show the Shroud doubled only three times.
But some months ago I cut out a photo of the Shroud and proved to myself that the Shroud can be doubled four times in such a way that it results in Jesus’ face in a rectangular segment of the cloth, in landscape aspect, exactly as it is in early copies of the Image of Edessa. Here I will show how it can be done, in what is a reasonable way to fold a long cloth, minimising strain at its fold edges.