This section is from the book "Modern Photography In Theory And Practice", by By Henry G. Abbott. Also available from Amazon: Modern photography in theory and practice: A hand book for the amateur.
Flash light photography is extensively practiced by amateur photographers with varying success. The majority of these photographs are failures, owing to the fact that the person or group is left in total darkness or nearly so and the sudden lighting produces a startled appearance on the faces of the subjects. Again the lighting is nearly always on one side, leaving the other side of the faces in deep shadow. In many of these pictures the effects are highly ridiculous, as some persons close their eyes when they catch the first glimpse of the flash while in others the pupils are so dilated as to have a very startling effect. To get good effects the room should be as brilliantly lighted as possible by means of gas or oil and the lights so placed as to soften the effect of the flash.
There are so many good flash lamps on the market that it would be presumptuous to say that this or that one is the best. Any of the modern lamps are good and when handled with care there is little or no danger. Accidents with flash lights are usually attributable to two causes, carelessness in the location of the lamp or the use of cheap or inferior flash light powders. When placing the lamp in position see that there are no lace curtains or other inflammable matter in close proximity to the lamp. As a rule the lamp should be somewhat higher than the lens. The person or group should be posed away from the wall as far as the room will admit in order to avoid deep shadows. A screen covered with white cloth and placed at an angle on the side opposite to the flash lamp but so it will not show on the ground glass, will tend to do away greatly with the harshness by reflecting light on the dark side of the faces. The gas or other artificial lights in the room should not be allowed to shine directly into the lens.
The posing being to your satisfaction proceed to focus on the ground glass. To do this you will have to place a lamp or candle close to the face of one of the persons in the center of the group. Use the largest stop, providing it will give you fair definition. The plate-holder is now placed in position, the slide removed and you are ready for the flash. We prefer the loose powder but the prepared cartridges now on the market give very good results. These cartridges are provided with fuses ready for lighting. Most of the modern flash lamps ignite the powder by means of an ordinary match. By pulling a trigger the match is ignited and forced through an opening in the back of the lamp by means of a spring, thus igniting the powder. At all times keep your face away from the powder. Never be in a hurry when taking a flash light picture. Do not be afraid of the light in the room fogging the plate but at the same time it is well not to draw the slide until you are ready to ignite the powder.
Sometimes a frame covered with tissue paper or cheese cloth is placed between the sitter and the lamp in order to diffuse the light but if such a screen is used a larger charge of powder is necessary. Flash lights are not only useful for night photographs but may also be used to advantage in the day time in making exposures of interiors, especially in large buildings and poorly lighted rooms. If judiciously used they are also a great help in portraiture during the day time, the effect being much softer than when used at night.
Silhouette pictures may also be made by means of the flash light. A screen of cheese cloth or sheeting is placed in the center of the room and the person or persons posed in front of it. The camera is then focused by placing a lamp or candle close to the face of the sitter, the shutter opened and slide removed. All lights are then turned low or entirely out. A flash lamp is placed on the opposite side of the screen from the subject or subjects and the flash made. The result will be a silhouette picture or black on white. These pictures may also be made by placing the screen close to a window and cutting off all light except that which comes through the screen. The person is then posed in front of the screen and the focusing and exposure done in the ordinary manner. As all the light comes through the screen, that side of the person next the camera will be in the dark and the result will be a silhouette. The largest stop will have to be used and when daylight is utilized a time exposure will be necessary, the time depending on the size of the screen and window.