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.
157. Why is it impossible to photograph a subject, with proper portrait effects, out in the open in broad daylight? Why is it imperative that any particular form of lighting or a special method of arrangement of light is necessary? Why is it impractical to place a subject next to a window, make an exposure and secure good results? These questions all lead up to the one vital subject of lighting and the control of the light.
Flat Effects Outdoors. If a subject were placed out-of-doors, in the shade, and an attempt made to photograph it, the resulting effect would be extremely flat, owing to the unlimited amount of light that would come from all directions. There would be no particular points of light on the subject that would stand out more clearly than others. Of course, light draperies and light portions of the subject will reproduce light, and dark parts will be dark in the photograph, but there would not be any perceptible amount of relief, or roundness, shown in the finished print.
First Steps Toward Controlling Light. True, characteristic and pleasing effects may be produced out-of-doors, but it is necessary that some methods or means of controlling the immense expanse of light be employed. For instance, it is almost impossible to place the subject in strong sunlight and expect to get a pleasing effect. It is necessary that the person being photographed be posed in the shade. As soon as this position is taken, action toward controlling the light begins. If the subject is placed on the shadow side of the house, the house itself acts as a curtain - shutting off the light from one side. Still, a flood of light will come from the top, so it is necessary to go a little farther and, perhaps, place the subject under a porch. Now two sides are screened from the flood of light, and if a background is placed at one end of the porch it would be possible to obtain a fairly pleasing portrait.
Flesh-Effects Lacking. Still, there will be too much light uncontrolled, causing the face of the sitter to appear quite flat, with no possibility of flesh-effects in the finished print, all of the high-lights being hard and the shadows lifeless.
Effect Of All Side Light. If the subject is placed in a room, quite near a window, with opaque shades pulled down from the top until the light comes in only at the lower half, all shadows will be cast straight across the face; the side next to the light will be in very strong light, while the opposite side will be in heavy shadow. The effect produced will, therefore, be quite contrasty and not pleasing.
162. Effect of All Top Light - If the other extreme is resorted to, the lower half of the window being curtained with some opaque material and the upper half left open, the light will fall on the subject almost directly from the top, heavy shadows being cast under the eyes, nose, lips and chin. The strongest light will, of course, be on the top of the head; the eyes will appear deeply sunken, and the whole result ghastly in appearance.