Practical Cinematography and Its Applications

by Frederick Arthur Ambrose Talbot

The Development of a Colony of Marine Organisms.

(Read from top to bottom and left to right.)

In the Marey Institute investigations with the convolvulus, which was placed on a chair a short distance from the lens of the camera, sixteen successive snap-shots were made in the hour. These pictures, taken at intervals of four minutes, show the complete opening of the flower, the phases in the successive pictures blending so well together as to convey the impression that the pictures were taken at the normal speed.

A striking contrast to the bulky, weighty, and massive apparatus employed ten years ago to photograph intermittently the opening of a flower is the latest device which is employed at this Institute for this work. It is a small, light compact contrivance driven by a kind of carriage clock. This clock actuates two levers whereby electric contacts are made at predetermined intervals to open and close the lens. This mechanism can be set so as to give exposures at intervals ranging from a minute to several hours, and will run for twenty-four hours without attention. The apparatus is as accurate as it is ingenious.

It is obvious, however, in such work, that a great deal depends upon the personality of the worker himself. If he is skilful he will find no difficulty in devising a reliable timing apparatus which he can trust for hours together. But the simpler the character of the appliances the more trustworthy will they prove, because the reduction in the number of the component parts will decrease their liability to derangement and irregular action.

Seeing that exposures have to be continued at the predetermined intervals throughout the whole twenty-four hours, arrangements must be made for artificial illumination during the night. This should not prove a difficult problem. There is a wide range of illuminants—electricity, gas, acetylene, etc.—from which a choice can be made according to the circumstances of the case. Thus a worker living in country districts may find a difficulty in obtaining electric current or coal gas, in which case he must rely upon acetylene, or a petrol gas flame, in conjunction with an incandescent mantle, or even an electric battery and flash-lamp with a reflector.

If electricity or coal gas are available from public supply sources there need be no anxieties whatever. A metallic filament incandescent electric lamp of high power is quite sufficient for the purpose, and if there is need for a concentrated strong light it can be obtained by mounting the lamp within a parabolic reflector, such as is used for automobiles. Coal gas with an incandescent burner and mantle is just as efficient, and concentration in this case can be managed in the same way with a reflector. But it is necessary to make sure that no draughts play upon the gas flame, as the intensity of the light might thus be greatly impoverished.

Acetylene is a very useful and powerful illuminant when all else fails. It is the nearest artificial approach to sunlight. Petrol gas with an incandescent mantle will be found just as good as ordinary coal gas, while there are many cheap lamps well adapted for its use. If all these alternatives are lacking there is the electric flash lamp working with the dry battery. A tiny metallic filament incandescent bulb mounted within a parabolic reflector will give a light of intense brilliancy. But the exhaustion of the battery causes the value of this light to diminish in a relatively short time, so it is well not to let it burn continuously. There should be a means of producing the flash only at the moment the timing apparatus makes the exposure. In one application of this system the flash and the movement of the shutter are controlled by an electro-magnet, arranged in such a manner that the lamp lights up a fraction of a second before the shutter is moved. Thus the object under study is in the full glare of the light before the film is exposed. Of course, if a high capacity accumulator can be obtained, such as that of the latest Edison Nickel type, the light may be left burning continuously. But when there is already an electrical system of actuating the shutter it is a simple matter to incorporate a means of limiting the contact in the lamp to the moment of the exposure.

For the average worker, however, the electrical system is too costly. He will usually prefer a form of light which can be allowed to burn continuously through the night. Even the longest night will not consume a very great quantity of current or gas. Also, unless some very accurate mechanism is used for controlling the intermittent operation of the light, there is always a chance that the exposure and the illumination may fail to synchronise, and thus an excellent film might be ruined.