How Light Falls on Form

Light behaves in predictable ways. Once you understand the pattern it creates on a simple form, you can shade anything convincingly, from an apple to a face. This lesson is one of the most important in the whole course.

The anatomy of light on a form

On any rounded form lit by a single light, you'll find the same zones, in this order:

1. Highlight: the brightest spot, where light reflects directly toward your eye. Its size and sharpness depend on how shiny the surface is.
2. Light: the area facing the light.
3. Halftone (midtone): the area turning away from the light. Values gradually darken.
4. Terminator and core shadow: the line where light ends and shadow begins. The core shadow is the darkest part of the form's shadow, right next to the terminator.
5. Reflected light: light bouncing back from nearby surfaces (the table, a wall) into the shadow side. It lightens the shadow a little, but it is always darker than any value in the light side.
6. Cast shadow: the shadow the object throws onto other surfaces.
7. Occlusion shadow: the darkest accent, where the object touches the surface and no light can reach.

Play with the light

Drag the light around the sphere and watch every zone move. Turn on "posterize" to see the form split into simple light and shadow families.

Two families: light and shadow

The most important division is between the light family (highlight, light, halftones) and the shadow family (core shadow, reflected light, cast shadow). Keep these families separate: everything in the light must be lighter than everything in the shadow.

Cast shadows

• A cast shadow points away from the light.
• It's darkest and sharpest near the object (the contact point) and gets lighter and softer as it moves away.
• Its shape follows the surface it falls on: it bends over steps, wraps around objects.
• A low light makes long shadows; a high light makes short ones.

Types of light

• Hard light (direct sun, a bare bulb): sharp terminators, sharp cast shadows, strong contrast.
• Soft light (cloudy sky, a window with curtains): gradual transitions, soft shadows, gentle contrast.
• Multiple lights: one main light (key light) and secondary lights (fill, rim). Beginners should study one light source at a time.

Planes on boxes

A box doesn't have gradients; it has planes. Each face gets one main value according to how directly it faces the light: the face toward the light is lightest, the face turned away is darkest. This "planar" thinking also works for complex forms like heads: simplify them into planes first.