Chiaroscuro

Chiaroscuro - used to depict volume, characterized by strong contrasts of light and shade usually affecting a whole composition.
My tutor recommended in his report for my assignment 3, that I include more mainstream artists to augment what is there. As an example he suggested I include some examples of chiaroscuro, particularly those of Rembrandt. The drawings by Claire Spencer are also good examples of this technique, as are those below, by Leonardo and Rembrandt.

Study for the Kneeling Leda

The shading above describes a quite linear form of chiaroscuro.

Leda's lower hand looks to me as though it is back to front - perhaps
she was a contortionist. Her lower right arm also looks thicker than the upper part.

- Just to illustrate that Leonardo was, of course, extremely accomplished at drawing hands and arms (above).

The Philosopher in Meditation 1632 - oil on wood 34x38 cm 

Rembrandt - The Philosopher in Meditation 

Here a dark frame curves around the entire foreground and perimeter of the painting. It branches off towards the seated figure from the left and again from the top right, reaching part way down the winding staircase, creating a mysterious void and producing an s-shaped movement within - echoed by partly lit areas of the staircase. This contrasts sharply with the glowing light from the window to the left of the philosopher, bringing him distinctly but softly  into focus. Another glow from the hearth on the lower right illuminates a woman's face and hands. The staircase gradually brightens and becomes clearer as it winds down and round towards the figure.
I found an interesting theory about the possible meaning behind the painting on the following link: http://dimahne.tripod.com/Articles/meditation.html