Now only that, But a photo has highlight and shadow history in it. One of the major aspects of 3D models is that when they are rendered, the program supplies its own highlights and shadows. If you already have them on the texture before rendering and the lights in your scene are coming from a different location from that of the original photo, you are probably going to get both.

It is difficult to find panametric photos, parallel to the plane of the face, that are lit to produce no highlights or shadows. So, adapting what you have requires that you fake this. And, although the sides of the head and body are unfolded, they are still fore shortened a bit.