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.
By the Prosch Manufacturing Co.
417. Much progress has been made in flashlight methods during the past few years. The old smoke nuisance is being avoided by the use of special fire-proofed bags, which retain the smoke and permit the light from the flash to pass through in diffused form. This revolution in method has been brought about largely through the introduction during the past few years of the Prosch Smokeless Flashbags and the Prosch Electric Envelope Flash Cartridge, both patented devices.
Various Flashlight Methods. It may be well to speak briefly of the other methods of flashlight work still in vogue. Among them, the pure magnesium blow-lamp process is a very efficient and necessary one for interiors and still life, and for commercial, sample, and catalog work, while the newer flashbag process is likely to be confined to the work of photographing people, and for interior work where smoke must be eliminated.
Magnesium Lamps. Pure magnesium blowlamps are made in many sizes and forms, prices ranging from $1.50 to $30.00 for a single lamp outfit. In these lamps pure magnesium (which is finely ground magnesium metal) is blown from a tubular reservoir up through a spreader, or V-shaped projector, in a wide, but very thin, sheet, through an alcohol flame, which, if the magnesium is of the proper grade and quality, completely oxidizes it, creating an intense white light. If not of the proper grade there will be some sediment of partially consumed magnesium. During the burning of this magnesium, the operator, who is holding the lamp in hand, walks to and fro behind the camera, raising and lowering the lamp to throw the light on every possible shadow that might be cast by the article being photographed. In commercial work (for which these lamps are used) flat lighting - that is, absence of all shadows - prevails, while in portrait lighting, side lighting must predominate to produce good modeling.
Flash-Lamps For Compounds. There are also lamps for using ordinary explosive flash powders. These are still more numerous in style, design and methods for igniting the powder. The methods for igniting explosive powder in these lamps require the burning of alcohol, which is extremely dangerous when used near such powder; burning ether, which is more dangerous; percussion caps; burning punk; all of which are limited to the firing of one lamp at a time. Electricity, however, is by far the safest and the most successful method to employ; and in addition it can be made to set off almost any number of lamps simultaneously. The development of the electric flash-lamp, by the Prosch Manufacturing Company, has led to the introduction of the Prosch Flashbag, which is shown in Illustrations Nos. 87 and 88.
Flashbags. The flashbag comprises, first, a fire-proofed, pure white muslin bag, made in peculiar form, extensible and collapsible by means of various styles of frame-work; second, a special style lamp made to ignite electric cartridges or loose powder by means of electric current; third, wiring; and fourth, switch-board necessary to carry the current to the bag-lamp and to control its use. The flashbags are generally used in sets of two or more, as the maximum amount of powder that can be set off with perfect safety in the ordinary flashbag is one-half ounce. A lamp of peculiar shape is necessary for ignition of powder inside the bag, as the flame must be directed straight upward so that it will not char the cloth. The patented form of lamp (which is a piece of sheet metal bent up against itself to form a long pocket), or the patented elec-
Illustration No. 88
Prosch Flash bags
See Paragraph 420
Illustration No. 89 Prosch
Illustration No. 90 Prosch
Photo by William H. Rau
Illustration No. 91 Banquet - Illuminated by Flashbags See Paragraph 432 tric envelope cartridge (which has the same form as the lamp described), make use of the only safe principles for a bag-lamp. These force the flame upward into a thin sheet of great area, which increases the illumination about 50%.