This is probably the most simple of the three (or so I suspect.) I understand there is probably information regarding this shot, but would like to make clear that I didn't use any footwork for this assignment. I just wanted to try to figure it out on my own.

For starters, the subject has a simple white background almost immediately behind. The background is translucent and is back-lit. The main and only source of light is probably the sun. The subject's back is facing the sun and the sun is positioned above the subject so the light helps to illuminate the top and hair of subject. 

The light is very even and shadows are hardly present. I imagine Avedon probably used a large diffuser over the subject to gain this look and may have created something of a large soft box for the subject to stand in.

I don't see why much more would have been used.