Hello Enzie,
The different prints are for playing with the cold warm contrast on the face. I think it is the most difficult part to obtain in a portrait. The computer is there, but basically I don't work from it if have enough prints... after a while my eyes just cannot apprehend a computer screen image as a source to resolve a problem on the portrait.
I would even say, sometimes, the worst is the photo the more interesting is it to work after it on a portrait... and clearly: no photo can replace the original model sitting for you hours and hours!
