Today our models were Patty Arquette, Valentino, Max and Oliver Twist. For our critique at the end of class I spent some time focusing on establishing over-all light and shadow. Specifically I mentioned the seemingly obvious fact that a highlight looks like a highlight because it is the lightest value in the drawing - so it follows that everything that is not a highlight needs to be darker than the highlight. Sounds obvious but not many of you are doing it. It is easy to get caught up in smaller features and miss the larger light logic of the scene.
In the first few minutes of the video below you can see a much more thorough demonstration of what I was talking about. He talks in terms of primary, secondary and tertiary forms while I tend to think of it in terms of "global" highlights and shadows vs. "local" highlights and shadows. The point is the same - you've got to establish (and maintain) the big picture before you get to the details.