CHAPTER X
SPEEDING-UP SLOW MOVEMENTS
The preceding chapter described how it is possible to photograph extraordinarily rapid movements and to slow down in projection so as to enable the eye to follow them. Now I will go to the other extreme and show how the very slowest movements can be accelerated and thrown upon the screen in continuous motion. This feature has proved one of the most popular in the whole range of cinematography, for it has enabled the public to follow, within the course of a few minutes, such wonderful and apparently impossible studies as the growth of a plant from the germination of the seed and the appearance of the leaves to the bursting of the bloom and the formation of the seed for the propagation of the species.
The speeding-up of relatively slow movements has become a favourite branch of research among cinematograph workers mainly because it is simple, inexpensive, and comparatively easy. The worker needs to develop only one special faculty. That is patience, for the recording of a single subject may easily extend over a period of a month or so, and the camera has to be kept going night and day to produce a faithful record. It is a field which the amateur can follow very profitably. It puts no great tax on his skill. The risk of failure is slight, and the films thus obtained, if worked out upon popular or instructive lines, are certain to command a ready market.
For this work one may use the ordinary £5 ($25) camera. It illustrates the fact that cinematography is nothing more nor less than a string of successive snap-shots, for the principle is that which is generally described as "one turn one picture." That is to say, instead of the handle being turned continuously as in taking a topical subject, it is moved at stated intervals, and only sufficiently to make one exposure and to jerk the film downwards the required distance ready to receive the succeeding image. It virtually resolves cinematography into ordinary snap-shot or Kodak photography.
This development, like many others widely practised in the moving-picture world to-day, has issued from the Marey Institute. It was there exploited in the usual manner for the study of natural movement and phenomena. In the early days of the present century, even before the picture palace came into vogue, the workers of this institution produced a short length of film showing the opening of the blossom of a convolvulus. Although this film is some ten years old it would be difficult even now to improve upon it. The opening movement of the petals is so steady and perfect as to suggest that the exposure was not intermittent but continuous.
In these particular studies success in the main depends upon the apparatus employed for the periodical exposure of the film and the judgment shown in deciding the lapse of time between the successive exposures. Naturally this varies according to the characteristics of the subject under investigation. A mushroom, for instance, demands exposure at briefer intervals than would be necessary for filming the growth of a grain of wheat. The timing is perhaps the most difficult part of the undertaking, because if it is not gauged to a nicety the movement on the screen is apt to be unnatural, the growth taking place in a series of sudden jerks instead of proceeding slowly, steadily and gracefully. Many a first-class film of this character has been ruined because the interval between the exposures has been too long to bring about the necessary blending together of the motions in the successive pictures. No hard and fast rule can be laid down to guide the worker. Experience and close study of the subject being photographed can alone enable this factor to be determined.
The auxiliary apparatus to ensure the exposures being made at regular intervals need not be of an intricate character. The simpler the means, the more likely is the result to be successful. Clockwork mechanism can be devised to open the shutter at stated intervals, but this system suffers from one serious disadvantage. The mechanism must be wound up regularly, and when a long study is in progress, extending over a fortnight or a month, the worker is apt to overlook this indispensable duty. There is one worker who generally uses a water motor, and has found it very reliable; but it cannot be safely left, and it ceases to act if the public water supply be cut off.
The most reliable agent for such work is electricity. When the Marey Institute first embarked upon these tedious subjects a very elaborate apparatus was employed. It was like a gallows, being in reality a massive wooden frame (see [illustration facing page 128]) fitted with a pulley. A rope passed over this pulley, and to one end was attached a weight P. The other end passed round a small winch T, to which the camera C was connected. Upon the spindle connecting these two parts of the mechanism was a small wing-piece L, one of the extremities of which rested upon a vertical spindle E connected with an electro-magnet F. In the electro-magnet circuit was a small water-balancer B having two cells and a see-saw motion. This was driven by a stream of water flowing from the tap of the tank R. The flow of water from the tap could be regulated.