This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
Pose. The first and most important matter for consideration is the way in which the head of the subject is posed. A tip of the head too far back or too far forward, leaning too much to the right or left, will make a wonderful amount of difference in the final result. The head should be held in a perfectly natural manner, as it is a very easy matter to exaggerate the neck of the subject, especially if of a lady gowned in evening dress or drapery. It is, therefore, necessary to be very careful as to the way in which you place the head.
The Eyes. The direction in which the eyes are turned is another point which must receive attention turned too much downward the model appears dreamy, while if the eyes are turned too high a strained and staring effect will be produced, the neck being exceedingly exaggerated in length.
The Lips. The lips contain a great deal of character, yet many times they appear to be glued fast and in such a position, are very unnatural. It is advisable to request your subject to moisten the lips with the tongue, which will restore their naturalness.
The Position Of The Body. The direction in which the body of the subject is turned is of equal importance to the posing of the head. The body should not be turned in the same direction that the eyes are looking. The lines of the shoulders and arms combine naturally with those of the neck and head, but this would not be the case if the body be placed squarely with the camera.
346. When focusing the image on the ground-glass be sure to provide for sufficient space for the subject to look into, and by all means avoid placing the head in the center of the picture space. This is extremely important and should not be neglected, for there is nothing so disagreeable as to see a face posed in profile with the nose almost touching the edge of the print. There must be enough space in front of the face to give your subject room in which to look.
Lighting. Although the pose is an important feature, the lighting is very essential in many profile pictures in securing pleasing results. The direction from which the light comes and the manner in which it falls on the face, are all important factors; therefore, due consideration must be given to both the pose and the lighting. The most successful form of lighting in profile portraiture is that which draws into prominence the strongest characteristics of the face of a subject. Thin face subjects are best made with a broad light, as with it better modeling will be obtained. Subjects with round faces are best portrayed in the Rembrandt or Shadow Lighting. If a front light is employed for round faced subjects the results will very likely be flat and give a very characterless portrait. As examples of portraiture the broad lighting effects on such subjects may not lack interest, but character studies will not be strong and convincing if the lighting is of this nature. For subjects with round faces which are also suited for profiles the strongest effect of relief is generally obtained by placing them in such a position that the light is slightly behind the plane of the figure, throwing the broad side of the face in shadow; or, as it is photographically termed, Rembrandt Profile Lighting.