The "one-turn-one-picture" movement has to be adopted for many subjects other than flowers. For instance, it is necessary in filming the movements of the star-fish, in evolution phenomena such as the emergence of a chicken from its shell, and in the case of certain minute organisms which can be cinematographed only with the aid of a microscope. But the same broad principles apply in each case; there is equal need for time and patience, while complete success can only be achieved by careful observation and ingenuity. There are critical moments in such work and the unexpected frequently happens. Unless the operator is equal to the emergency weeks of tedious labour may be wasted.
The study of exceedingly slow movements offers a very promising field to the patient worker. A film which occupies a month to photograph, and entails an exposure once every thirty minutes, produces a film only 90 feet in length. In projection it passes across the screen in a minute and a half. This means that a process of Nature is condensed into one thirty-seven-thousandth part of the time it actually took, and its presentation on the screen is a remarkable triumph. But at first sight the minute and a half seems a very slight return for the time and labour expended. This is one of the principal reasons why the professional cinematographer displays a marked aversion to the recording of slow movements. On the other hand, it offers unique attractions to the private investigator, for the time occupied in preparing a film that reveals the wonders of Nature invariably commands a high price if it has the elements of popularity or novelty.
CHAPTER XI
CONTINUOUS CINEMATOGRAPHIC RECORDS
It has already been pointed out that the intermittent method of taking cinematograph pictures results in the loss of certain motions which occur during the interval when the lens is eclipsed by the shutter. A similar loss is experienced by the eye, in daily life, when it blinks. In the case of blinking, of course, the proportion of movement which escapes observation is exceedingly small. But in cinematography practically one half of the movement is lost. When very rapid movements are being investigated these losses become appreciable—in fact the most vital part of a motion may be missed during the 1/32 part of a second during which the lens is covered by the shutter.
There are many fields in which cinematography as at present practised is quite useless owing to this intermittent eclipse of the lens. Suppose that the behaviour of a rapidly moving piston rod is under observation. With the ordinary type of moving picture camera and process the results are quite misleading. The piston travels so rapidly, perhaps at a rate of 8,000 lineal feet per minute, that with sixteen pictures per second only a very small proportion of the work would be recorded.