This is a demo that I did for the class this morning. I wanted to show how I would block in the main value masses quickly to get the design down before the shadows shift too much. The photo below is the scene a few minutes before I started. You can see how the line of sun on the ground in from of the chapel is still there. By the time I started blocking in, the sun had moved toward me, making the shadow from the tree move a bit. I like it better as a more solid shape.
I probably spent an hour doing this demo while talking and explaining what I was doing and taking a quick break.
It is important to block in all of the light and shadow before the light shifts. If you wait and tackle it one piece at a time the shadows will be inconsistent throughout the painting.

Frank Gardner © 2009

Frank Gardner © 2009
I'll post more about the class as I have time.