High-quality art and low-quality art can often be separated by shading. Realistic shading makes any image in either black and white or colour come to life. Because natural and artificial light sources in everyday life create shadows around everything, realistic art should also include these shadows. When teaching shading to art students, it is important teach them the principles of shadows before they exercise their new skill.
Instruct your art students to sit around a table. Set up a table lamp. Turn off any overhead lights and turn on the table lamp. Set different objects in front of the table lamp and show the students how the light cast from the lamp creates highlights, mid-tones, shadows and cast shadows on and around the object.
Move the lamp to show the students how as the angle of the light changes, the angles and lengths of the shadows also changes.
Teach the students about the different elements of shadows and shading. When a light is shone directly onto an object, the face of the object illuminated by the light is called the highlight. This is the brightest area. Partway back from the highlight of the object is the mid-tone, which is the object's area receiving a portion of the light. To the rear of the object is the shadow, which is receiving no light. Finally, the object creates a cast shadow onto the table or whatever surface it occupies.
Instruct your students to draw a circle on their paper, then indicate to them that a source of light is coming directly from the left side of the circle. Have the students add shading by holding their pencils on an angle, using the long side of the lead rather than its point. If the students have understood your beginning tutorial, they should indicate light in the highlight area, light grey in the mid-tone area and dark greys in the shadow and cast-shadow areas.
Instruct the students to draw other objects, and perform the same exercise of adding each element of the shading. When the students have mastered how to add realistic-looking shading to simple objects, they'll be able to add shading to more complex images, such as faces and scenery.
Remind students that if they cannot determine how a shadow is cast on a particular object, they should try to work out the shadowing by holding a light to a replica of the object and noting where the shadows fall. For instance, if a student is shadowing a face, she can aim a flashlight at her own face, look in a mirror and observe the shadows.