By F. J. MORTIMER, F.R.P.S.,
Editor of the " Amateur Photographer " and " Photographic News."
The production of photographs by magnesium light, commonly known as flashlight, is possibly one of the most fascinating phases of modern camera work. It places a new power in the hands of the photographer, and renders him independent of daylight, but at the same time it is probably a form of photography that is little known and less understood by the average picture maker. It is not a difficult branch of the art, although its pitfalls are numerous. It is, however, because of its apparent simplicity that disappointing results are so frequently obtained.
These results have commonly been produced by those workers who have not thought of the rudiments of the subject, but have started with the mistaken idea that flashlight has singular properties of its own not peculiar to other forms of lighting.
There are, of course, instances where certain subjects can only be treated by means of flashlight, but these are thus treated either because of their environment of time and place, or because daylight is not possible, or inadmissible, i.e., flashlight work in mines, stage photography, etc.
To start at the beginning, therefore, a general rule to be observed is that, apart from the actinic value of the light used, the most successful and pleasing effects are always obtained if the conditions, as regards the direction of the light, arc made similar to those followed in daylight portraiture. Ninety per cent, of flashlight negatives are of portrait or figure subjects. Eighty of those ninety can usually be recognised immediately as flashlight productions, and their characteristics are not in their favour. They appear harshly lit, with crude shadows and hard cut-out outlines. Why is this ? Simply because the methods of lighting that would have been employed had daylight been the illuminant have been ignored.
F. J. Mortimer, F.R.P.S. By Furley Lewis, F.R.P.S.
Were it possible to focus the subject on the ground glass, illuminated by the actual flashlight, these errors of lighting would not occur. Experience, therefore, will be the chief guide for the flashlight photographer, and a method of trial and error his most practical instructor.
THE LIGHT. This may take the form of either a flash lamp or a flashlight mixture - ignited by the application of a spark or flame. The flashlight is, of course, generally used at night.
Magnesium is usually the base of most descriptions of flashlight. Magnesium wire or ribbon is of very little use for the purpose, as it burns but slowly and its illuminating powers are restricted. In the form of powder or dust, magnesium burns very rapidly when brought in contact with a flame and gives an intense white light. It can be made to burn even more rapidly and completely if intimately mixed with some chemical substance rich in oxygen - such as chlorate of potash, but as these mixtures really constitute explosives they should be treated differently from plain magnesium powder and never used in a flash lamp.
The best form of flash lamp for general purposes is that known as the " blow-through." It consists of a reservoir with the lamp attached. The reservoir contains a supply of pure magnesium powder. A sufficient quantity of this powder to make a flash is blown through the flame of the lighted lamp. The flame is formed by burning cotton wick or other suitable substance soaked in methylated spirit, and is attached to the orifice through which the magnesium is blown. Pressure on a pneumatic ball attached by a tube to the reservoir serves to blow a charge of the powder into the flame to make the necessary flash.
With some lamps an accumulator for the air, similar to that on the familiar scent spray, is used to drive a continuous stream of magnesium into the flame and so produce a prolonged light.
The application of a lighted taper to a flashlight mixture causes a brilliant and instantaneous flash, but to ensure the best results the mixture should be spread on a train of gun cotton.
Gun cotton or pyroxylin is sold by most photographic dealers and chemists, and is quite safe to handle under ordinary conditions. Its use is advocated as not only ensuring a more complete combustion of the flash mixture, but also because the best results are obtained when the light is spread over a broad area. The flash is also more rapid.