Read Stephen Jones’ posting on his blog and study the graphics.
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.