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.
Preparing The Window. In preparing the window it is necessary to provide a diffusing screen. This diffusing screen is really a light-controlling screen and should be attached to the window in such a manner that it can be readily raised or lowered.
Light Controlling Screen. See Illustration No. 11. This screen should be made in the following manner: Make a light frame, using strips of wood about 1 1/2 inches wide by 1/2 inch in thickness. For the ordinary house window, this frame should be about 30 inches high, and the exact width of the inside of the window casing, allowing for slight play. Stretch four wires across the frame - two across the center, two inches apart, one across the top, and one at the bottom of the frame. Attach the wire to screw-eyes, stretching from one screw-eye to another. Next procure two yards of white cheese-cloth about 30 inches wide.
Dyeing Cheese-Cloth In Coffee. Dye the cheesecloth a light coffee color. This can be very easily accomplished by boiling the cheese-cloth about 10 minutes in strong coffee, to which has been added a heaping teaspoon-ful of salt. Rinse the cheese-cloth in clear water, and allow to dry. With the light tan stained cheese-cloth the softest grade of diffusion can be obtained, securing the mellow high-lights which are so important in artistic home portraiture.
Diffusing Curtains On Controlling Screen. Cut the cloth in three parts, so as to make two sets of curtains, three sections to each set. Make allowance for at least a one inch hem at top and bottom. String the curtains on the wires, having them hang in folds, and quite full. For a thirty-inch window you will require a width and a half for each section. The full width should be split to form the third section. After stringing the curtains fasten the wire to permit them to slide smoothly.
Hanging Screen In Window. On the upper edge, in the center of this frame, insert another screw-eye. At the top of the window and close to the sash attach a small self-locking pully. Fasten one end of a long cord to this screw-eye, and run it through the self-locking pulley. By pulling or releasing the cord the diffusing screen can be raised or lowered at will. A screw-eye hook may be substituted in place of the self-locking pulley. In that case, however, attached to the side of the window casing should be a button, to which the cord can be attached when the diffusing screen is properly adjusted. (See illustration of window screened).
Two Light Controlling Factors. All lace curtains should be removed or drawn back from the window, allowing only the opaque shade or spring roller to remain. The spring roller shade can be raised or lowered, as desired, to cut off top light that may not be required. With the opaque shade and diffusing screen in operation, absolute control of every ray of light entering the room through this window will be at the disposal of the photographer.