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.
Selecting A Window. Before attempting to make At-home portraits, it is necessary to have a few pieces of apparatus to assist in securing proper lighting effects. The first consideration lies in selecting a window from which to derive the source of light. A window facing north is best, as much more uniform lighting may be obtained from a window with a northern exposure. A north window is always free from strong sunlight, the illumination being soft and diffused at all times of the day, and, therefore, easily controlled.
Unobstructed Light. The light should not be obstructed by trees, porches, or other objects, and the higher and larger the window, the better will be the general results. The great advantage of having a high window lies in the fact that exposures can be made further from the source of light, thus obtaining more diffusion.
Avoid Reflections. The sun shining on the window through which the source of light is admitted will cause a reflection upon the subject. Unless this reflection is overcome in some way, it will be impossible to control and concentrate the light, which will be necessary in order to produce a correct Plain Lighting. For this reason the use of a window facing the north is advised, as the sun will never shine on it, which insures complete absence of reflection. If light is secured through a north window there will be no need for diffusing the light, other than with the diffusing screen.
How Windows Facing South, East Or West Can Be Made Use Of. If a room containing a window facing the north cannot be secured, any unobstructed window can be made to do by diffusing the strong sunlight with cheesecloth, or thin bleached muslin, stretched over the entire window. The cheese-cloth is employed to subdue the strong sunlight, reducing it to about the same conditions as light coming through a north window. In order to control the light the regular diffusing screen must be used, in addition to the cheese-cloth. On account of the light constantly changing, it will be found to be more difficult to produce good results with a window upon which the sun shines than one with northern exposure. If a room with a north window cannot be procured, it will be better to select a west, or even an east light in preference to one facing south. If a west light can be had, the necessity for screening the windows can be obviated by working in the forenoon, as the sun will not interfere until later in the day If an east light is employed use it after the sun has left the east side, or during the afternoon. In this way artificial diffusing of the harsh sunlight can be avoided, and results as good as may be secured with a north light can be obtained. Of course, when it is necessary to use the light at all times of day, and other than a north light must serve, use the screen while the sun is shining, and remove it when there is no direct sunlight on the window.