This little portrait (7 x 8.5") was created from a 3.5 x 5" vintage photo. I don't normally consent to doing such a small human portrait, especially from a client provided reference. I prefer to photograph the subject myself. It allows me to see the subject clearer. What is her attitude about things? Does she have a sense of humor? From the many photos I take, I will be able to make compositional choices that allow me to say something specific about the subject. With one client reference I have nothing but a 2 dimensional image. There is no way to know the subject. Hence I meticulously copy, as best I can, the photo. This kind of interpretation leaves very little, if any room for creativity. I depend on the medium and the character of my technique to make the difference. Though, I carefully warn the client that to work this small makes it difficult to nail likeness, that all it takes is one tick of the pencil to completely change an expression, does she hear me?
Once the piece is finished and a photo sent off for approval, I sweat it out. Did I communicate well; did I capture whatever it is the client sees as likeness or will I have to start over again? Weighing challenge against risk, did I quote the proper price? One could say, that each time I do a commissioned piece I learn something new. That is invaluable right? I've been doing portraits for 15 years. It should be effortless by now, 
(smiley face with tongue in cheek and wink.) Good thing I have another commission to get to!