Volume is the term used to refer to an objects height, width and dimension. Achieving the illusion of volume is crucial if you want to give your drawings and paintings a realistic look. And to create the illusion of volume, you must focus on value. In fact, most dimensional objects, if lit by a single light source, can be broken into five values.
To see how this works, set up a group of objects and position a single light source above and to one side of them. Notice that each object has a dark and a light side, and that there are five distinct value areas for each objectthe highlight, the value of the object in the light, the core of the shadow, reflected light and the cast shadow. The highlight is where the light source hits the object at full strength. Its also the only place where pure white is possible. Everything else in the painting should be darker than the highlight. Objects with slick surfaces, such as chrome, have hard-edged highlights. Conversely, textured surfaces such as burlap or skin dont have hard-edged highlights. Slightly darker than the highlight is the value of the object as it appears in light. If the light source changes this value may change, but the highlight wont.
As the object moves away from the light its value darkens. Everything on the dark side of the object will be darker than the light side of the object. The darkest part of the shadow is called the core. Youll find it where the object turns away from the lightnot at the back of the shadow. The core of the shadow takes the emphasis away from the outer edge. When the core is defined and the outer edges of the form softened, the illusion of bulk is particularly strong. The area just beyond the core of the shadow contains reflected lightlight that bounces off another surface into the back of the shadow. This area of the shadow is always darker than it appears. Although its darker than the light side of the object, it often seems lighter because its surrounded by dark values.
The cast shadow is the final component of volume. In the example below, this is the shape of dark shadow cast by the object onto the table. A cast shadow is always opposite the light source and is created by the object blocking the light. So the cast shadow is the darkest of all shadow areas. Cast shadows are usually darkest where an object touches the table. The shadow lightens gradually as it moves away from the object.
Volume is most obvious when you use a single light source, as shown in the drawing above, right. By carefully lighting your subject and consciously applying the five-value approach, you can breathe life into virtually any basic shape.
Joanne Moore is managing editor for The Artist’s Magazine.