Sketchbook - Learn to see
Value
Value is the term used to describe light, gray and dark tones.
All neutral tones from white, black and all the gray tones between are called achromatic, meaning having no color. All tones that have some color are call chromatic. When investigating art in all its components, you must consider the relationship of value to other art elements, color, line texture and shape. All these elements must exhibit some value contrast in order to remain visible.
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.
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.
Note how the same mid-tone value patch looks different when placed on backgrounds of contrasting values.
Chiaroscuro and Illusion
Value describes volume and depth of space. In Europe artists of the Renaissance were concerned with showing depth and volume in opposition to the artists of the Middle or “Dark Ages.”
Renaissance artists manufactured the term “Chiaroscuro” to describe how light and dark can imply depth and volume. The word Chiaroscuro is a combination of two Italian words that mean light and dark. (chiaro (clear, light) + oscuro (obscure, dark) Atmospheric or Ariel perspective was one of the artistic strategies used in the study of Chiaroscuro during the Renaissance.
One of the most used and useful applications of value is creating the illusion of volume and mass on a two dimensional surface. When a mass is exposed to light, a solid object will receive more light from one side than another when that side is closer to the light source.
A spherical surface demonstrates this as an even flow tone from light to dark. A cast shadow is created when the source of light is obstructed by the sphere. An angular surface shows sudden contrast of light and dark.
Intuitive Space is merely a trick the artist uses to create depth on a two dimensional surface. Intuitive methods of space control include overlapping, transparency, and other applications of spatial proportion.
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 – squinting at the subject to see value definition affected by figure-ground making value relationships clearer.
The Light Side of the Shape
Highlight
The lightest spot or streak is where the light strikes the subject in exactly the middle of the light side between the shadow edge and the edge of the object. A highlight can be shinny and crisp on a glass or metallic surface, or fuzzy and muted on a dull or textured surface.
Light middle tones
Note, to avoid confusion, “always” keep the values on the light side lighter than the values on the dark side. In reverse, the values on the dark side are darker than the values on the light side. It’s the middle tones on either side that confuse the artist’s eye in value relationships
The Dark Side of the Shape
“Shadow edge” or “core shadow”
The edge where the light is blocked from the light source is the darkest value on the dark side. The core or darkest value blends into the middle tones from the shadow edge on round subjects.
Dark middle tone
The variable values blended form the shadow edge on the dark side. Again, the dark middle tones are darker than any values on the light side. The human eye can trick the brain into believing the lightest values on the dark side are the same as the darkest values on the light side. If the artist is confused about lights and darks, the rendering is less understandable.
Reflected light
If the object is sitting on a white table, the light from the table reflects back onto the object and makes the shadow side lighter.
If the object is resting by something black or dark, the middle values will become a dark reflection.
The concept also holds true when the object is sitting on a colored surface.
The Cast Shadow
When the source of light is blocked by an object it casts a shadow.
The length and shape of the cast shadow depends on the placement of the light source.
Long shadows are cast from a side light source (as from the sun in late afternoon or early evening), and short cast shadows are cast from over head (as from a noonday sun).
The shape a shadow casts depends on the shape of the object casting it and how close source is to the object.
The vocabulary used to describe cast shadows in art come from shadow descriptions in astronomy. The umbra, penumbra and antumbra are the three distinct names given to the description of shadows cast by heavenly bodies.
The umbra is the darkest part of a shadow considered the absence of light.
The penumbra is a lighter outer shadow where the object is only partially obscuring the light.
The antumbra is more obscure. When it is visible it seems to extend out from the penumbra in a lighter and less distinct way.
Light Source, Cast Shadows and the Axis
Too many complex cast shadows can be confusing. Such objects can be rendered by blurring the edges.
Cast shadows of irregular shapes and in natural sun light are open for interpretation because of the constant changing sunlight: As you work on location, the sun will continue to advance and change what you are drawing.
Note the place you would have the sun be positioned, and keep that constant to avoid a confusing spread of shadows. The nature of shadow is affected by weather, sunlight, moonlight, or artificial light.
Objects Have Light, Medium or Dark Values
Objects have an allover light, medium or dark quality. To make your representation more believable, you should take into consideration the light or dark value of each object. Before you render details, block in the value characteristics of each object. Using this strategy will save you time and achieve a more realistic result.