Originally Posted by David Lyga
...or do the facial characteristics matter in this determination?

Fat faces, thin faces, faces with large features in proportion to the head size, handsome faces, homely faces...HOW MUCH COMPACTING DO WE WISH TO IMPART?

For 35mm, the 'proper range' runs from 80mm through 105mm. Some even swear by, (or swear AT), the mighty 135mm. But what is REALLY the best way to determine this flexible number in order to optimize the results? Do different faces require different aspects? This is a question that is not parsed too often because the 'literature' gets into the way of challenging theory. - David Lyga
How far away do you want to be? That determines your perspective. Then choose a lens that frames it the way you want without wasting a bunch of film area.

If you try to figure it out with mathematics it is very complicated, because, as you know, angle of view changes as you focus closer. That effect is greater with bigger format cameras.

A head-shoulder picture with a 20x24" camera is taken under conditions where the viewing angle is about one-half that of the angle of view at infinity. A head-shoulders picture with a Minox is taken under conditions where the angle of view is nearly identical to that at infinity.