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.
The Perpendicular Light. In Illustration No. 1, Fig. 1, we present the perpendicular light. We question if any photographer would employ such a light from choice, in preference to other styles. Sometimes, however, the building selected for the location of a studio will not admit of other than the perpendicular style of light. Usually this style of light is not large, generally running from a point a few feet from the floor to the level of the ceiling. Sometimes an office building containing large windows is selected, and the windows serve as the light to be employed for supplying the required illumination. Under such conditions the photographer is somewhat handicapped, as only bust portraits or two-third length figures can be made successfully under such conditions. Groups are practically out of the question. A photographer handling a light like this would naturally cater to an exclusive class of trade, to which bust or two-third length figures only would appeal.
31. In Figure No. 1 is shown a perpendicular light, 6 ft. square, built 3 ft. above the floor and running very close to the ceiling. Owing to the size of the light, with its limited power of illumination, the subject must necessarily be arranged quite close to the source of light. The light is controlled by means of thin muslin curtains, dyed a light tan color, which when properly arranged may be adjusted to produce any effect desired.
Arranging The Curtains. Stretch three sets of curtains crosswise of the window, each set overlapping the next about four inches. Divide each set of curtains into three sections. This will enable you to open any portion of the light required. When the light is soft, or diffused, no curtains at all will be needed. If the light is too strong in some places, by drawing a portion of one or more sections over such spaces the light will be diffused sufficiently to overcome the objection. With a little care, beautiful portrait effects can be produced and lightings of any kind obtained.
Controlling A South Light, Or Any Light Where The Sun Shines On The Glass. There are different ways of controlling strong sunlight, but the following method has proven most practical: The skylight should be curtained with opaque shades, top and side, exactly the same as for a light with a northern exposure. These opaque shades are necessary for controlling the angle of light. For diffusing the sunlight, Irish mulle or muslin of a light tan color may be employed. The muslin is dyed a light tan by boiling in strong coffee, to which has been added a tea-spoonful of plain salt. The salt sets the color. Boil the muslin for about 10 minutes, or until it becomes a light tan color, when it may be rinsed in clear water and dried, after which it should be smoothed out with a hot iron. The tan curtains are then arranged on the skylight, in place of the white muslin diffusing curtains previously referred to.
34. When the sun is shining brightly on the skylight, by stretching these curtains the light becomes diffused and mellow, and while the direct light may be quite strong, even when filtered through these curtains, it is of such a color as to produce soft high-lights instead of strong, chalky effects. These curtains, of course, should be used in connection with the movable diffusing screen. By means of this movable screen you control the light on the subject still further.
Glass For Skylights. In most modern skylights the glass is either ground, hammered, or ribbed. Occasionally, however, the photographer is compelled to work under a skylight of plain glass, which, naturally, will work quite contrasty. To overcome this contrast and obtain a softer light, the glass may be coated on the inside with a thin application of starch paste, or some other like substance. (See Chapter XLVII (An Inexpensive Studio), Vol. VIII, "An Inexpensive Studio.")