The Anatomy of Shadows

Christy Olsen

What lurks in the shadows? A higher contrast of lights and darks than any local color. Shadows tell us a lot. Sometimes, the form or shape of an object is revealed more by its shadow than by the object itself.

The Anatomy of Shadows

Form vs. Cast Shadows

In representational art, there are two types of shadows: form shadows and cast shadows. The form shadow is found where the object turns away from the light source on the object itself. It includes the core shadow and reflected light.

Always ensure that every form of shadow has a well-articulated core shadow to tell the viewer where the object turns in space. Core shadows are essential in creating an object's volume or structure.

Cast shadows are created by the object, blocking a single light source or spotlight, which "casts" a shadow underneath or behind it. Every cast shadow can be broken down into three different tones.

The Anatomy of a Cast Shadow

The umbra, penumbra, and antumbra are three distinct parts of a shadow created by any light source after impinging on an opaque object.

The UMBRA (Latin for "shadow") is the fully shaded inner region of a shadow cast by an opaque object. It is the innermost & darkest part of the cast shadow. It includes the occlusion shadow, which is directly underneath the object. It is closest to the object, where the object itself entirely blocks the light.

The PENUMBRA (from the word "paene," Latin for "almost, nearly") is the partially shaded outer region of the shadow cast by an opaque object. It is the region where some light sources leak back in due to reflected light. Light bounces off of other objects or even the surface underneath, and it starts to contaminate the shadow. It becomes lighter than the umbra region.

The ANTUMBRA (from the word "ant," Latin for "opposing") is the region from which the occluding body appears entirely within the disc of the light source. It is the lightest region of the cast shadow and has the softest edges of all three zones.

A great way to mentally check your drawing or painting is to use the "Shadow Checklist.' Make sure that the shadows have all of the following characteristics.

Shadow Checklist

1. DARK - Shadows are "darker than," not just DARK or a darker version of the local color. Ensure the reflected light is darker within the form shadow, or the structure could fall apart.

2. EDGES – Shadows have softer edges, even more so in the cast shadow than in the form shadow. As the cast shadow moves further away from the object, the edges become softer and softer.

3. ECHO - Form shadows echo or mirror the form of the object they represent (i.e., a form shadow on a sphere has a round shape; the rounder the shape, the more concave the form shadow should be).

4. PASSIVE – Shadows are passive. They have little or no texture. Smooth-out brush strokes or pencil marks compared to the lighted texture area.

5. ARTICULATED – Cast Shadows should have a definite and well-articulated shape. Sometimes, an object's form reads more from its cast shadow than its local color.

Shadow Diagram
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