The visual element of value or tone is, in its simplest form, the juxtaposition of light and dark. It is defined as the intensity of lightness or darkness in anything that is visible.
Value, along with hue and saturation, make up the three components of color.
In nature there are hundreds of different steps in value that are sometimes not easily distinguished by the human eye. In the graphic arts and photography, however, there are far fewer steps because they are simply to subtle to perceive visually. Images derive a simulated natural tone from pigment, paint, or nitrate of silver. Thirteen steps in value have been identified, which range from white to black. These steps are based on a tonal scale, which defines the variations of shading.
A work composed mainly of the lighter end of the scale is a "high key" work, for example, the landscape works of Claude Monet. While "low key" works, such as those of Rembrandt, are made up of the darker end of the value scale.
The element of value is used to express emotions, form, space, and movement as well as to give off the illusion of light. Since the scale for value is so limited in two-dimensional images, it is implied through several techniques. The juxtaposition of elements within a work determines value. This is achieved by placing the lightest element next to the darkest. One way to comprehend the importance of value is to count the shades in an image from lightest to darkest.
Each color has its own tonal value; as pink is lighter than brown. An image is often described in terms of its value and chroma. Chroma is defined by the other two elements of color: hue and saturation. Value is independent of, and exists without, chroma. Both the element of value and the elements of hue and saturation (chroma) create their own patterns. Often these value patterns cross and camouflage chroma. A monochrome image depicts the importance of value in a work. This type of image is composed of different degrees of value for one color or a few complementary colors.
In real life, value is upset by texture because surfaces react to illumination. Since in nature things are obscured by shadows, artists developed techniques to show this notion. Sfumato is the technique of using graduated values to blur images and to make them ambiguous, as well as to suggest movement.
Another technique that allows artists to manipulate the element of value is chiaroscuro. This contrast technique exploits the difference between light and dark.
Value is not, however, perceived in absolute terms. Instead, it is perceived in relative terms, in which degrees of value are influenced by their surrounding environments. Specifically, contrast effects change the perceived values of an image or object by the juxtaposition of adjacent darker or lighter tones. Value is one of the most fundamental visual elements, as without variations in light intensity images and objects could not be perceived by the human eye.
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