American cinematographer (Jan-Dec 1931)

Twenty AMERICAN C I N E M A T 0 C R A P H E R September, 1931 Sound Pictures and Solar Problems (Continued from Page 9) other instruments for the more customary eclipse observations were set up at these stations. A great deal of consideration was given to the matter of landmarks which could be identified in the pictures of the shadow. Huge crosses of canvas were suggested, and whitewashed areas and buildings, in addition to the natural features of the landscape. All these were used to some extent, but in the end we relied chiefly on pairs of 25,000 candle-power flares, suitably placed and set off by alarm clocks. By placing these pairs of flares, some parallel to the central line of the computed path of the shadow and some perpendicular to it, and by spacing them differently in certain patterns, we could identify any pair in any frame of the picture. Eventually, two large planes, each with two experienced pilots, were placed at the service of the expedition. One was a tri-motored Fokker cabin plane and the other a large Fairchild army plane. The Fokker, assigned to the Ramm's Ranch station, was equipped with a first-class motion picture camera, and flew from Mather Field. A place on the dry bed of Honey Lake was chosen as the base for the army plane. In this plane were installed the sound camera with its amplifiers and batteries and the radio receiver. Arrangements were made with the Navy Department to broadcast time signals each second during the period of totality for this region. A number of test flights and exposures were necessary so that all the complex manoeuvers of observers and instruments could be tried out and coordinated, the pilot, for instance, handling the plane so that the camera could follow a train on a curved track. All this was accomplished from Clover Field where the instruments were installed in the army plane under Captain Stevens who commanded the plane, and who, being himself a skilled aerial photographer, aided the sound camera expert by operating the camera. On the day of the eclipse heavy clouds covered both sides of the mountains throughout the period of the eclipse. Only through breaks in the clouds were glimpses of the pageant seen from the ground. From the air, the sight was marvelous indeed. The plane from Mather Field, finding clouds over Ramm's Ranch, flew westward over the predicted path, as had been planned in case of such a contingency and took pictures of the country below, though not quite sure of the shadow, battling with cold and exhaustion at an altitude of 19,000 feet. Interesting pictures they are, taken through scattered clouds, but the shadow of the moon could not be defined in them. The flight of Captain Stevens and his two associates in the army plane was even more dramatic and, I believe, also historic. The story is recorded in Pomona College publications — how they waited under the clouds, all ready to go, until hardly an hour remained to reach the great altitude required; how at last a small clearing appeared, and they took off, pushing up through this hole, through a mile-depth of clouds, and then came out above them; how they climbed still higher until they reached 18,500 feet, just in time to swing into position as totality began; how they blanketed their instruments to keep them warm and themselves to keep from freezing; how they had to conserve their oxygen supply; how they saw the shadow appear in the distance and rush on toward them; how they beheld it appalled, not realizing at first what it was; how they got their pictures in spite of every difficulty; and how they came down at last, through the clouds, to a safe landing on the dry lake bed — a thrilling story as told by Captain Stevens and his companion, James W. Balsley. For the first time in history those men saw the great shadow of the moon coming upon them with terrific speed across the surface — not of the ground, alas — but over the upper surface of the clouds. For the first time motion pictures were taken of this phenomenon as the shadow came and went. Astronomically, of course, we were disappointed that the shadow was not seen upon the ground where its exact position could be determined, instead of upon the rough and billowy surface of clouds where its outline was too vague to be well marked in the film, although it may be readily followed on the screen. Great as our disappointment was at the time, we know now that, while leaving much to be desired, the expedition was far from being a failure, as I shall point out in a moment. So far I have spoken of one of the two problems in which our expedition was chiefly concerned. Let me now, much more briefly, refer to the second problem. In this we undertook to measure the intensity of the sun's radiation, especially the intensity of the sunlight itself, at a number of points in a line across the path of totality. Five such points some 500 yards apart were selected at Ramm's Ranch, in a line perpendicular to the computed central line. At each point an instrument was placed, consisting essentially of a photoelectric cell and amplifier, and a milliameter whose index marked the changes in intensity of light as the shadow passed over the point during the partial and total phases of the eclipse. All these milliameters, each connected by long lines to its distant photometer, were mounted upon a panel at a central station together with two timepieces, so that all these ammeter dials and clock faces could be photographed simultaneously by a motion picture camera — by two of them, in fact. In this way a continuous picture was taken showing the variation in light intensity at each point, and graphs were plotted for each point. The net of these curves, then, not only locates the path of totality, but tells much more as to the intensity of the radiation and illumination. At the national meeting of the A. A. A. S. in Chicago, last August, where the work of this expedition was reported to the Astronomical Section, it was agreed that two things were accomplished that were quite worth while. The solution of two entirely new problems had been undertaken. In both cases a new technic was proposed and tried out, establishing a new method which might be tried again with good hope of success even though the conditions would not be so favorable again for perhaps a hundred years. Already we are considering a repetition of the experiment with the eclipse of August, 1932, in New England. This paper was presented at the 1931 Spring meeting of The Society of Motion Picture Engineers, and is published here through the courtesy of the Society's Journal. ♦ Mitchell Announces New Rolling Tripod AN addition to the rapidly-swelling Mitchell line is a new rolling tripod for studio use. Unlike most devices of this nature, it is scarcely heavier than a standard cinema tripod, yet it is capable of supporting even the heaviest silencing "bungalows" now used. The height of the camera is controlled by a single crank, which by means of a triple-extension, telescopic support allows an unusual range: the lens of the camera may be dropped to within a yard from the floor, or raised to a height of nearly eight feet, with perfect stability at all positions. The head mechanism is the standard Mitchell friction head, with its telescopic arm, enlarged and strengthened to operate perfectly with even the heaviest of "bungalows," some of which weigh several hundred pounds. Due to its small size, and unusually great extension, this device should find favor in studio use, as it is sufficient for most uses, and therefore makes it possible for a single unit to replace three or four less flexible ones of varying sizes. In addition, as the device is equipped with standard Mitchell tripod legs, it may be used away from the studio, on location, very satisfactorily.