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.
Groups. Groups should be arranged in a semicircular form, facing the camera. Each member of the group should be exactly the same distance from the camera. In case of groups of a dozen or more members some of them may be seated, others may be arranged standing. Usually the tall members appear best in a sitting or lounging position. If it is necessary that any of the subjects be seated on the floor, the legs should be drawn in closely - not extended toward the camera.
Important. It is always best to have the room well lighted when making flashlights. Especially is this advisable when making portraits or groups, for if the room is darkened the sudden flash of the powder so strains the eyes of the sitters that they almost invariably have a staring look. On the other hand, if the room is already well illuminated by electric or lamp light, the strain will not be great and the eyes will have a natural expression. When the room is brightly lighted, however, the shutter should not be opened until just an instant before the flash is made. It must also be closed immediately after the flash.
694. When more than one flashlight is to be taken the windows should be opened and time allowed between each flash to free the room thoroughly from smoke. If this precaution is not taken, those pictures which are made while there is smoke in the room will have a foggy appearance. No matter how little smoke there is in the room it may cause a fogged negative, as the lens is even keener than the eye in detecting it.
695. The flash-sheets are not instantaneous, and, therefore, when making portraits or groups you should request your subject to remain still, just the same as for a time exposure. The flash-sheets are best to use when photographing general interior views in which there are no moving objects. From one to two seconds are consumed in burning a single flash-sheet, and the light is much less brilliant than the instantaneous flash. This is a decided advantage when the subjects can be depended upon to keep quiet, as the eyes are not strained by the flash and do not have the staring effect so often seen in flashlight pictures. In photographing children or groups it is better to use the flash-cartridge, or the flash-lamp, as either of these methods is practically instantaneous.
Development. When developing negatives that have been made by flashlight, you should keep them as far from the ruby light as possible. In fact, it is advisable to shade them from the rays of the ruby light. The reason for this is that the image will not appear as quickly on such negatives as on those made by daylight. Development might proceed a little slowly, but you should judge completed development in exactly the same manner as you would ordinary exposures made in daylight.
Practice Work. It is advisable for your first practice work to use the minimum amount of powder given in the scale, and if upon developing the plate you find it under-exposed, you will understand that more powder must be used, when working under the same circumstances, and the exact additional amount must be estimated by the appearance of the quality of the negative first developed. For your first experiments it is advisable to select the interior of a room, locating your camera so as to take in as much of the room as possible; then arrange your flashlight ready for the exposure.
698. Above all things when handling flash-powder, whether in sheets, cartridges, with a flash-machine, or an ordinary tin pan, keep cool, work carefully, and never hold your hands or face over the powder at any time. When all is in readiness, first press the bulb and open the shutter, and with a lighted match or candle (usually a tape is used) light the fuse. As soon as you have done so turn the face from the light, looking into the direction of the view of the room, to observe the effect of the illumination. As soon as the exposure is made close the shutter or cap the lens.
699. With a little experience you will be able to work the flashlight as well as daylight, even with groups and portraits in the home. When developing flashlight plates use diluted developer, and carry the plate to a good strength. Make proof prints from each experiment, noting on the back of each all data concerning the manner of procedure, such as the amount of powder, the size of stop used, size of room you are working in, color of the surroundings, method of igniting the powder, etc. File all proofs containing data in your proof file, for future reference.