The shroud as model for portraits of Jesus
Before the rediscovery of the the shroud in the 6th century the depiction of Jesus was arbitrary.
Example:
(Abb. in Whanger)
After the rediscovery of the shroud, portraits of Jesus have almost been standardized:
Same church (San Vitale, Ravenna), but some years later (picture in Whanger)
Here some examples of the always same type of image, derived by the Shroud of Turin:
Coin of the Emporer Justinian II. (Image in [C], (c) Whranger )
Jesus Pantocrator (Sinai-Monastry )