Exploration of a Sphere Part 1: Types of Shadow and Light

One of the most basic core doctrines of learning to paint in a representational way is to learn how light behaves and how to paint it.  Enter the good old sphere or egg.  Now art schools make students draw or paint them until the students run away screaming.  The problem is that students are never taught the point to all this boring work.  The students are just annoyed by what they think is busy work.  So I am going to do a week long series on our simple friend the sphere to attempt to explain the point.  Every object in existence that you may want to paint can be split up into combinations of spheres and planar shapes (like a cube).  It is as simple as that.  I will do a post in the near future illustrating this point.

But first, before we can combine simple objects into more complex ones, we need to understand how light behaves when it falls upon a simple object, like our good old sphere:

I set up a wood sphere on a piece of paper with a desk lamp lighting it from the side.  This is what is termed "form revealing" light.  This light creates a clear distinction between light and dark on the sphere, thus revealing its shape.  If we moved the light around so it was shining directly on and from the front of the object, it would reveal no shadows (think a picture taken with a flash).  This would flatten our sphere out so it looked like a paper cutout.  We want to make things easier on ourselves, so we want to use form revealing light.  Think chiaroscuro or Rembrandt lighting (more about this in a later post).

Rembrandt van Rijn, Self-portrait, c. 1629; Germanisches Nationalmuseum, Nuremberg

See the strong difference between light and shadow?  This is form revealing light.  Anyway, back to our sphere, which we want to also be lit with form revealing light:

Under this lighting we can see:
a highlight
the core shadow
the reflected light
and the cast shadow

The highlight is fairly obvious, it is the lightest part of the sphere, where the strongest light is directly hitting it.  More on the other kinds of light and shadow tomorrow.

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One of my students asked:
I was reading your blog (loving it) and I have a question on the figure painted by Rembrandt.  Is there reflective light under the figure's left eye? Thanks. 

Ooo, good question!  As the reproduction above looks, the answer could be yes.  It is darker than any of the lights on the light side of the face.  However, from my experience looking at Rembrandt lighting, that triangle under the left eye should be lighter.  It is illuminated by the main light source falling on the left cheek, not light being bounced off something.  You can just see the shadow cast by the nose on the left cheek, which ends before the triangle of light begins.  I suspect that the image above is not a great picture.  Rembrandt's paintings are notoriously difficult to reproduce.  I went looking and lo and behold:

Rembrandt van Rijn, Self-portrait, c. 1629; Germanisches Nationalmuseum, Nuremberg

That is better.  So the answer is no, that triangle under his left eye is direct lighting (but reduced a bit because it is further away from the light source).  The reflected light on the left side of his face is that bluish greenish gray tinge you see along the edge of his cheek, jaw, and under his chin.