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.
Too Much Top-Light. The subject is placed too near the center of the skylight. The sitter must be removed from under the light a trifle farther than for either a Plain Lighting or a Rembrandt Lighting. If there is not sufficient space between the end of the light and the end of the room, cut off a portion of the light rays by drawing one of the opaque curtains down the entire length of the top-light.
Softening High-Lights. This difficulty will occur if you do not handle the diffusing screen properly. When first placing the diffusing screen in position, close all curtains; then experiment by moving the screen nearer to, or farther from, the subject until general diffusion is obtained. Then separate the curtains on the top row slightly, when white light is to be admitted for the catch-lights With a little practice no trouble will be experienced in securing the effect desired. At times it may be found necessary to use the black curtains; at other occasions simply the tan curtains. The necessity may arise also when it will be advisable to draw a section of the white curtains over the skylight to soften harsh lights.
Securing Roundness. Lack of roundness will result from using too small a source of light. Atmosphere and roundness will be produced by first flooding the entire skylight room with light and then softening the light on the subject, using only the diffusing screen. Place the background far enough away from the subject to secure the proper amount of diffusion.
Background Too Sharp. The background is too close to the subject, or too small a stop is used. The background should not be less than three feet from the subject, and no smaller stop than is actually required to give clear definition should be used. Another difficulty which may be experienced may come from using a background which is painted too sharply. Avoid purchasing a ground of this kind, as soft, delicately blended ones may easily be procured.
Reflector. The same rules govern the handling of the reflector for this lighting as are applicable to any other lighting, yet if the skylight room is painted a light color you may be able to dispense with the reflector altogether. By all means avoid too strong a reflection of light, as this will produce glary effects, destroying both half-tones and shadows. For angle of reflector, see diagram of floor plan. Illustration No. 20.
Shadows Fall Straight Across The Face. If the shadow cast by the nose falls straight across the face, the trouble lies in using too much side-light. Raise the curtains on the side-light and use more top-light. Remember, the greater the distance the subject is located from the side-light, the lower will be the angle of illumination. Be careful to place the subject so that the light will fall from the front. For that reason, it is essential that the sitter be placed back from the end of the skylight and not under it. The light should fall on the subject at an angle of 45°.
Securing Proper High-Lights, Or Catch-Lights. To secure snappy high-lights, first diffuse the light on the subject's face, until the desired softness is produced. Then open the diffusing screen slightly here and there, just enough to produce high-lights, or catch-lights, wherever desired.
No Catch-Lights On Shadow Side Of Face. The trouble lies in not having secured the proper angle of light, and in having the face turned too far away from the source of light. The light must fall at an angle and the face turned so that the tip of the nose blends into the shadow side of the cheek. This will then allow the strong light to spread across the cheek and give a highlight shaped like the letter V, on the shadow cheek, the highest and broadest part being at the top of the cheek bone, from there slanting down to a point almost directly opposite the base of the nose. Turn the subject so the light will catch the shadow cheek and if more side view of the face is wanted, move the camera nearer to the light
Little Or No Shadow On The Shadow Side Of Face. If the skylight room is painted light, and too free use of the reflector has been made, little or no shadow will be visible, and the result will be entirely flat. If this occurs, dispense with the reflector altogether, and if too much reflected light still comes from the walls, place a medium dark background between the. wall and subject. The walls of a skylight room should never be painted white. Dark, slate-colored walls will save a great deal of trouble by overcoming reflection. Placing the subject farther back from the skylight will supply more shadow.