British Kinematography (1951)

March, 1951 WESTON: FILM IN RESEARCH 85 1. Detailed, accurate and permanent Records Simple film records of events contain a wealth of detailed information and at the same time eliminate the personal errors and41 discriminations of human observers, and provide a permanent record for close study at leisure. The author recently made some records of cells growing in tissue culture, and the film contained so much information that in order to analyse the speed of move ment of only a sample of the cells in the field (without taking into account theii directions of ' movement), a single workei was engaged whole time for more than 2 week. Film records of such events as the explo sion of an atomic bomb2 are examples of this type of film. The film record is available for detailed examination when repetition of the event itself is impossible. 2. Automatic Operation The motion picture camera can be used when it is not possible to employ human observers. It will withstand physical conditions which might be fatal to a human being and it can be accommodated in a very small space. Recent films of the surface of the earth taken from rockets, or the facial expression of aircraft pilots during powei dives, are well-known examples of work of this nature. 3. Use with Optical Instruments Work in this class includes the use .of the motion picture camera in conjunction with the microscope, the telescope and certain other optical instruments, such as the interferometer. Very little work has yet been done in conjunction with the telescope, though recenl films of solar prominences made by Lyot and others are among the most wonderful re search films that have ever been made. Work with the astronomical telescope is exceedingly difficult, and the economic factcr alone certainly limits the amount of film produced per annum. The interferometer has also been used particularly with the microscope, to investigate the action of solvents on plastics, but this practically exhausts the list of optical instruments that have been used with the motion picture camera to date. 4. Simple Interpretation Many recording instruments provide a record which requires interpretation before it can be used for study and is, in conse quence, difficult to explain to a layman. Kymograph records are of this type, and also the very complex records of the electroencephalograph. The majority of film records, on the other hand, are easily understood and appreciated by a non-technical person. This is of the greatest use in industrial research where, foi example, high-speed films of machines have to be shown to business executives. Such films speak for themselves with ease and conviction. 5. No Mechanical Interference The fact that the making of a film of an event does not interfere mechanically with the object under observation is often of very great vplue. As examples of this may be mentioned the recording of the gaits of small animals and insects,3 and the bursting of bubbles. Circumstances do occur when it is difficult to avoid some interference with the object being investigated, for example thermal effects and the like, but it is unusual not to be able to find some way round difficulties of this kind. In certain classes of biological work, however, the mere presence of light may have a very disturbing effect on the animal being studied, and cases of this kind are very difficult to handle. They are, fortunately, quite rare. 6. Measurement of Time and Acceleration Provided the speed of the motion picture camera mechanism is known, the resulting film, can be used for timing and measurement purposes. The measurements most frequently required are: — (a) duration of an event; (b) velocity of an object; (c) acceleration, either linear or angular.