The Anatomy of Shadows

The Anatomy of Shadows
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 the object itself.

Form vs. Cast Shadows

There are two shadow types in representational art, form shadows, and cast shadows. The form shadow is found in a place where the object turns away from the light source on the object itself, it includes the core shadow and reflected light. (see the Anatomy of Light & Shadow).

Always make sure that every form shadow has a well-articulated core shadow to tell the viewer where the object turns in space. Core shadows are an important feature in creating the volume or structure of an object.

Cast shadows are created by the object itself, blocking a single light source or spotlight, which "casts" a shadow underneath or behind it. Every cast shadow can be broken down into three separate 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”) 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 light is completely blocked by the object itself.

The PENUMBRA (from the word “paene,” Latin for “almost, nearly”) the partially shaded outer region of the shadow cast by an opaque object. It is the region in which some of the light source is leaking 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

Shadow Diagram
1. DARK - Shadows are "darker than", not just DARK or a darker version of the local color. Make sure 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 that 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, in comparison to the lighted texture area.

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

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