A Theory of Light and Shade

color theory
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  A Theory of Light and Shade © January 2009 Sheri Lynn Boyer Doty  All Illustrations for a theory of light and shade are by Sheri Doty accept for Manet’s   painting “The Railway” showing an undefined light source. Before you undertake your practice of the use of light and shade in your art you need to understand the significance that light and dark contrast has in making a painting or drawing visually believable. Value is the term used to describe light, gray and dark tones.   Johannes Itten wrote “the contrast between light and dark is one of the most expressive and important means of composition.” Value contrast can be encountered in both colorful and non -col orful art renderings.” 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.  A simple Value Scale shows figure-ground relationship s 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. Click Image For Larger View   Chiaroscuro   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.” Men of the Renaissance considered their time period to be the Age of Reason and rebirth of artistic and mathematical achievements. 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. (Atmospheric or Ariel perspective is covered in depth in the section “Objective Color Harmony”.)   Chiaroscuro and the Illusion of creating intuitive space.   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. Click Image for Larger View   Intuitive Space is merely a trick the artist uses to create depth on a two dimensional surface.   “Intuitive space”  is merely the illusion space created by using artistic methods to trick the viewer into seeing depth, volume and mass on a two dimensional surface. Intuitive space is sensed or ”felt” on a two dimensional plane. Intuitive methods of space control include overlapping, transparency, and other applications of spatial proportion. In a “Theory of Light and Shade” I will show how to create intuitive space by using “Light Logic”.  Light Logic refers to how light interacts with objects. Light Logic is the term Betty Edwards uses in   her book “The NewDrawing on the Right Side of the Brain”     Light Logic and the Rendering of Three Dimensional Objects onto a Two Dimensional Surface.   You will make your art more believable when you keep these basics in mind.  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. Click Image For Larger View 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.  A Light Side and a Dark Side on Round or Circular Surfaces   When one light source is present, I was taught the dark side is “always”darker than the light side of the object and the light side is “always” lighter than the dark side. Establishing a definite light side and dark side makes round objects appear round and defines the form of an object accurately. Use this simple trick to make your artwork more true to life, separalight tones avoiding figure-ground confusion. Click Image For Larger View   Click Image For Larger View   THE LIGHT SIDE IN TWO PARTS   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 in Three Parts      Click Image For Larger View   Form Shadow in Three Parts   “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 being painted 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 of the painting is resting by something black or dark, the middle values will become a dark reflection. The concept also holds true when the object of the painting is sitting on a colored surface. If the reflected light is reobject. Cast Shadows   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 closource is to the object. Click Image For Larger View   CAST SHADOWS IN THREE PARTS   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. Click Image For Larger View   Light Source, Cast Shadows and the Axis  
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