American cinematographer (Jan-Dec 1934)

358 American Cinematographer 0 January 1934 HERETOFORE 1 6mm cinemicrographers have been limited to reproducing their microscopic subjects m monotone, with the result that many subjects so filmed lose much of their real value. The amateur has at his disposal one of the best color methods available, requiring but little technical knowledge to reproduce colors in a truly accurate and lifelike manner. The application of this process to cinemicrography opens to him not only the beauty of form and rhythm, but of color as well. Apparently the amateur experiences difficulty in combining the optical principles concerned. It is not the purpose of this article to go into all of the technical phases of photomicrography, or to describe the optical principles involved in the Kodacolor process. This information is available from other sources, if not already known by the amateur. There are two methods by which the Kodacolor process might be applied to cinemicrography. One method requires special optical equipment for projecting the image directly on the film. This optical equipment is not available to the average amateur. The other method herein described, is quite simple and inexpensive requiring little knowledge of optics or photography. The entire set-up consists of seven units, i.e. (a) a laboratory microscope, (b) a Kodacolor equipped cine camera, (c) carbon arc and water cell, (d) photographic ground glass, (e) an auxiliary lens of approximately 3 inch focal length, (f) a suitable support for these units. The microscope is placed upon a solid platform and above it is mounted the cine camera. The optical systems of the two instruments are centered as near as possible by inspection. Above the microscope eyepiece and approximately seven inches below the camera lens, is mounted the ground glass screen (d ) . The illuminating system consists of a carbon arc so adjusted as to throw a beam of light through a water cell to the microscope sub-stage mirror, which in turn directs this beam up through the lens system of the scope and produces an image of the object on the ground glass. The water cell is filled with distilled water which removes most of the heat from the light and prevents damage to lenses and preparations. Due to the fact that an optical bench, in the usual sense of the word, is not used in this set-up, it is necessary to place a thin ground glass disk, usually supplied with the microscope, in the holder provided below the sub-stage condenser. This disk diffuses the light sufficiently to assure even illumination throughout the entire microscopic field. The ground glass screen (d) is an ordinary 5x7 ground glass which can be obtained from any photographic dealer. To a large extent the quality of the image to be photographed depends upon this screen, as its function is to pick up the image projected by the objective and eyepiece lenses of the microscope. In order to pick up this aerial image it must diffuse the light to a high degree. This diffusion is necessarily accomplished by the individual grains of the H i Symbols in this sketch are explained in text Experimenting screen surface. Naturally this diffusion destroys much of the fine detail within the projected image and it is certain that this detail, the essential component of all photomicrography, once destroyed cannot be restored by the camera lens and film emulsion. To be more precise, the problem of detail is one of resolving power. The criteria of such work is to resolve as fine detail as possible, being limited only by the resolving ability of the microscopes optical system and the film emulsion itself. In addition to this problem is the one of illumination. This is more apparent when one realizes that the Kodacolor filter has an exposure factor of approximately 35X and this factor is extremely evident in any attempt to make Kodacolor movies by artificial light. These problems, ground glass grain size and the light absorbed by it, can be met in two ways; first, by a reduction in grain size or second, by doing away with the ground glass entirely. As previously stated, the latter method can be done, but requires optical equipment not within the range of the average amateur. The author has met this problem by the simple expedient of treating the ground glass screen with ordinary mineral oil and wiping the surface almost dry. This treatment tends to fill up the spaces between the individual grains and effects a reduction in diffusing ability, as well as increasing to a great extent the amount of light transmitted by the screen. However, there seems to be a limit as to the amount of oil that should remain after wiping. Too much tends to destroy the image completely by making the grains non-existent, too little tends to destroy detail and increases light absorption. The exact amount