The Theory of Light and Shade


Guest blog written by Sheri Doty

A simple Value Scale shows figure-ground relationships

 

Figure-Ground is the condition in which backgrounds tone or hue changes the visual impact of the figure resting on it. The same hue or value appears to be a different depending upon the contrast of tone or hue of the background upon which it is placed. Conversely, two different tones or hues appear to be the same when placed on contrasting grounds. Each will have an impact on how believable your art will be perceived by the viewer. Most people have difficulty perceiving “figure-ground” relationships. When the same medium toned figure is placed on varied light and dark backgrounds, it will be perceived to be as a different value.Example: When a medium gray is placed on a near black background, the mid-gray tone appears very light. When the same gray tone is placed on a near white background, it is perceived to be very dark. But when a mid gray tone is placed on a similar value background, the contrast is minimal. Note how the same mid-tone value patch looks different when placed on backgrounds of contrasting values.

A Light Source and Shadows

A light projected onto an object or figure creates lights, darks, and cast shadows. Your source of light may be the sun, the moon, a light through a window or an artificial light. When several light sources are present the light and dark tones vary and are less predictable. To simplify the study of light and shadow in this first section, I will use only one light source.

Two Kinds of Shadows

There are two kinds of shadows that occur when one light shines on an object, a cast shadow and a form shadow.

 

Cast Shadow

When an object blocks a light source it casts a shadow. A cast shadow is not a solid shape but varies in tone and value. The farther a cast shadow is from the object which casts it the lighter and softer and less defined becomes its edges.

Form Shadow

A form shadow is the less defined dark side on an object not facing the light source. A form shadow has softer less defined edges than a cast shadow. Form shadows are subtle shadows essential for creating the illusion of volume, mass and depth. The changes in form shadows require careful observation – quinting at the subject to see value definition affected by figure-ground making value relationships clearer.

Value as Pattern

Controlled shallow space is illustrated by the early cubists such as Picasso and Braques. Their paintings are taken from realistic subject matter and abstracted into unified flat tonal planes. The planes are shaded individually with the semi-illusion of space with no light
source. Later, each plane takes on characteristic value combined with other planes with the same style of value pattern. This produces a carefully conceived two dimensional pattern of light and dark values. The shallow space develops a three dimensional effect through the characteristics of the advancing and receding values.

More next week from Sheri Doty, who is an accomplished painter and faculty member at Salt Lake Community College and Peterson’s Art Center.