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March, 1951
WESTON: FILM IN RESEARCH
91
equipment for a comparatively modest expenditure.9 Earlier workers, such as Dr. Commandon and the late Dr. Canti, used the conventional microscope with both lightand dark-ground illumination, but neither method was all that could be desired for that difficult object, the living cell. The recent development of the phase-contrast microscope has revolutionised the study of the unstained and living cell, and this has
great advantage over 35 mm. film. With suitable emulsions, the resolving power of the microscope with a 16 mm. camera need be in no way inferior to work done on 35 mm. film, and about one-eighth of the light may be used. Standard 35 mm. film may possess some advantages when working with low magnifications and large fields, in which case very much less light is necessary and the risk of cell damage is small.
'ig. 7. High-speed Camera Set-up for use with the Compound Microscope.
brought about a renewed interest in films made with the microscope.
The 16mm. Film
The use of 16 mm. film for this work is not to be considered an economy or as a second-best, but as a technical necessity.
Since living cells are very sensitive to radiant energy, and may indeed be killed by it quite easily, it is essential to work with the smallest possible projected microscope image, as the small image will be brighter than a large one, and 16 mm. film offers a
A few workers only have used the microscope with the high-speed camera, as the technical difficulties and cost are increased. Professor Otto Storch, of Vienna, has studied the movement of cilia and ciliated organisms, using camera speeds up to about 120 pictures per second, and the author has recently done some work up to 3.000 pictures per second, but in this case the magnification was not high and no difficulty was experienced in' obtaining sufficient illumination.
Since the microscope increases the apparent velocity of a moving object, the increase