Show them examples of abstract and realistic portraits. Discuss why some artists developed a realistic style for portraits while others favored abstraction. Focus on a realistic example and have the students explain what makes it look real. Introduce the idea of proportion . Proportion is one of the principles of art and design.
Proportion is the relation of one object to another in size, amount, number or degree.
In other words, artists wanting to create a realistic portrait must figure out how big to make each facial feature in relation to the others. They must also place each face shape in the proper place. Artists make studies or practice sketches to solve proportional problems. They may make many sketches before attempting a final portrait. Explain that students will each make several sketches and a guide or reference sketch about face proportion that they can keep and refer to when they begin their final drawing.