Study the Portrait of Himself, by Albrecht Dürer. You will find no affectation here; the most simple and direct brush-work only. You will not be able to do this sort of thing, but that is no reason why you should not try for it. It will depend on the brush-stroke. It implies a precision of eye as well as of hand. It means drawing quite as much as painting,—drawing in the painting. You will not get this great precision; nevertheless, try for it, and get as near it as you can. Don't try for too much cleverness; be content with good sincere study, and the most direct expression of planes that you can give.
Let your brush follow lines of structure. Don't lay on paint across a cheek, for instance. Notice the direction of the muscle fibre. It is the line of contraction of the muscle which gives the anatomical structure to a face. If your brush follows those, you will find that it takes the most natural course of direction.
Do the same with the planes of the body and of the clothing. Note the lines of action, and the brush-stroke will naturally follow them.
See that the whole form, and particularly the head, "constructs." The head is round, more or less; it is not flat. The planes of it cross the plane of the canvas, recede from it, cross behind, and return. This in all directions. You must make your painting express this. It is not enough that there be features, the features must be part of a whole which is surrounded, behind as well as in front, by the atmosphere. The hair is not just hair, it is the outer covering of the skull, and of necessity follows the curves of the skull; and there is a back part to the skull which you cannot see, but which you can feel—can know the presence of, because of the way it is connected with the front part by the sides. All this you must make evident in your painting, as well as the facts which are on the side of the skull turned toward you. How make it evident? By values and directness of brush-stroke.
Background.—Never treat the background as something different from the head. The whole thing must go together. The slightest change in the background is equivalent to that much change of the head itself. For the change means necessarily a different contrast, either of color or light and shade, and it will have its effect on the color or relief of the head.
Paint the two together, then. Make the head and all that goes with it or around it as equally parts of the picture, which all tend to affect each other. Your background is not something which can be laid in after the head is finished. True you can paint the background immediately around the head first, and then, after painting the head, extend the background to the edge of the canvas; but the color, tone, and character of the background must be decided upon at the time the head is painted, and carried on in the same feeling.