The ideal proportions of the human head are well established in artistic tradition, based on the classical ideal of Greek and Roman art. When first gaining an understanding of the human form, the traditional rules of proportion are worth knowing, like the basic breakdown of the main structure of the head. However, while it is useful for roughly positioning the key points of the face, to achieve a good likeness, it is important to closely observe the structure of your individual sitter. These proportions give you a starting point, but you have to adjust the structure—sometimes quite a bit—to suit the individual.
Note that the eyes sit about halfway down the head. A common mistake is to make the forehead too short. The base of the nose is about two-thirds of the way down the face.
The distance from the forehead to the back of the head is about the same as the distance from the top of the head to the chin. Squashing the back of the head is one of the most common errors when drawing the profile view.
The face divided into thirds and halves
When drawing from life, the change of view between your eyes can be confusing. Try closing your nondominant eye when positioning foreshortened details in the face, and be sure to keep your head very still, as a slight change of position dramatically changes the view.
Note that babies and children have much higher foreheads and the distance is shorter across the nose and chin, particularly before their teeth come in.
Use the “thumb and pencil” method to assist with judging relative proportions of your model. Visualize imaginary lines through the corners of the nose, eye, and eyebrow, and check them against your drawing. You'll be surprised how quickly the likeness of your subject begins to take shape just by locating the key structural points of the face.
Across the simple basic structure of the head are many subtle changes of plane. Some of these are more obvious than others, such as the jaw line or creases in the edges of the nostrils. Some, such as cheekbones or the bridge of the nose, will be obvious from one viewpoint, while from another they will seem to disappear. A typical snapshot view, with the sitter squarely facing the camera or viewer, is probably the most troublesome, as key planes are foreshortened and the face appears broad and flat. Add to that poor lighting, and you'll be in for a tough time. With just a slight change of angle, you have a far more opportunities to develop the structure of the face. Sure, the foreshortening through the eyes and mouth when the face is at an angle can be tricky, but it's worth the effort for the opportunity to clearly model the planes of the head.
