This was an awesome 30 minute pose. Not only for the great negative and positive shapes formed by his body, but the dramatic lighting and interesting cast shadow. The shadow was very important in establishing his weight and the direction of the spotlight. The only spot I don't like right now is the relationship between his chin and his shoulder - too close in value.
For the longest pose of the light, we moved the light to two different sources (both of wich blinded at least one artist who was trying to draw, but o well - the light looked good!) One was high and over his left shoulder, the other was on the floor, throwing light upwards onto his torso creating very complex patterns on his chest.
I was working with charcoal pencil on a tan piece of paper, adding light cream and a bit of white towards the end. I like the change in height from the left shoulder to the right, and the way he is sitting into his left hip. The sense of weight on the chair feels pretty good. Again, I wish I had worked larger, but I'm glad I captured all of the back.