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.
Lighting Hard. The flashlight was too concentrated, too near the center, and not sufficiently diffused. Diffuse the light through muslin or similar cloth stretched on a frame, or use a secondary source of light. In any case, neither should be too near the object or subjects.
Lack Of Detail In Shadows. This difficulty will be experienced if the light is too concentrated, too near the sitter, or insufficiently diffused. If the correct amount of powder has been used, and the instruction in the preceding lesson carefully followed - and a reflector used to illuminate the shadow side of the face - a full amount of detail should be easily obtained.
Eyes Of The Sitter Closed. The subject, by watching your movements, knew approximately the moment you were going to make the flash, and the eyes were instinctively shut at the moment of exposure. Whenever possible, the ordinary illumination of the room should be maintained while making the exposure. It is a mistake to turn down the lights, as the eyes used to darkness are sure to shut or appear unnatural when the flash is made. Subjects should always be advised to look away from the light so as to receive the illumination more from the side. This will give more of a Portrait Lighting and will also overcome the closing of the eyes during exposure.
Misty, Foggy Appearance Of Portrait. The light from the flash has been reflected onto the lens and has fogged the plate. See that the flashlight is clear of the angle taken in by the lens. If not, shield the direct rays from the camera, and see also that the light is not reflected into the lens from mirrors or picture glasses. The smoke from a previous flash, if hanging about, even if only faintly visible will produce an effect of fog. Lower the windows and open the doors after an exposure. This will create a draft and carry off the smoke.
Portrait Flat And Lifeless. The lighting has been too much in front of the sitter, and probably too low. The best position for the light is at an angle of 45 degrees from the sitter. The light should be at least 8 feet above the floor for a standing figure. A three-quarter side lighting, with reflector, gives the best results. Too much powder, or working the reflecting screen too close to the subject, will give flatness.
Flash-Compound Refuses To Ignite. The powder is damp. Flash-powder should be kept very dry and handled carefully. Be sure you have not used pure magnesium in place of flash-powder.
Flash-Lamp Explodes. A flash-compound has been used in a lamp intended for the pure magnesium metal powder. The greatest of care must be exercised in this respect, and under absolutely no circumstances use a flash-mixture in a closed lamp which is intended only for pure magnesium powder. If in doubt as to whether the powder you are using is magnesium or flash-powder, test a small quantity of the powder before using it in the machine, by placing a small amount of powder on a pan and igniting it with a match or long taper. If the powder explodes with a Hash it is flash-powder you are using; if it cakes up and only flickers it is magnesium powder.
No Image On Plate. If upon attempting to develop the plate, you find that after a sufficient length of time no image appears, the trouble is no doubt due to the fact that the shutter was not open when the flash took place. It is advisable to experiment in manipulating both the shutter and the lamp (without having the lamp loaded) so as to become thoroughly accustomed to the manipulation. It often happens that one also forgets to draw the slide of the plate-holder.
Focus. Sometimes trouble will be experienced in securing a sharp focus, owing to the lack of illumination in the room. Especially is this true when working at night. All of the ordinary illumination of the room should be used, and if this is insufficient to properly illuminate the face so that you can see it distinctly on the ground-glass, have some one hold a lamp, match, or candle close to the subject's face. If a group is being photographed, a lighted candle may be held by the member in the center of the group and the member at each end, and you can then sharply focus on the flame of the candle. Always focus with the lens wide open.
Proper Amount Of Powder To Use. The required amount of powder is governed by many different conditions - the color of the walls and ceiling of the room, the distance the lamp is from the subject, size of stops, speed of plate, etc. In the lesson proper we have given approximate amounts of powder to use under varying conditions, but the exact amount can only be ascertained by trial. A record should be kept of each and every exposure made, so that you will be able to profit by previous experience.
Magnesium Lamp Chokes Up. This difficulty will be caused by not giving that even, steady pressure to the air which forces the powder into the flame uniformly. A few repeated trials will give you a perfect idea as to the manner of operating this kind of a light. The magnesium lamp should be cleaned each time immediately after use. If this is done there will be little danger of the lamp choking up.