Journal of the Society of Motion Picture Engineers (1930-1949)

not move during the exposure so the resolving power of this camera may be high enough to validate data obtained at a 450 per sec rate. In conclusion, the use of high-speed cameras for metric purposes illustrates a common experience — equipment well suited for one specific purpose may be entirely inadequate for a similar purpose. The extremely high frame speeds possible with the Fastax and Eastman High-Speed cameras are usually useless for metric ballistic purposes because of the accuracy limitations of the cameras and film. It has been necessary to design metric cameras with these accuracy limitations in mind and use them in ways that minimize their errors. Greater accuracies can be achieved only if emulsions and lenses can be developed which permit the use of shorter exposure times and which at the same time possess higher resolving power. References 1. T. J. Obst and J. A. Clemente, "The Bowen ribbon-frame cameras," NAVORD Report 1273, NOTS 343, U.S. Naval Ordnance Test Station, Inyokern, Calif., Jan. 15, 1951. See also, for general description: E. E. Green and T. J. Obst, "Bowen ribbonframe camera," Jour. SMPE, 53: 515-523, Nov. 1949. 2. John Titus, Mary Driggers and Laurence Minvielle, "Methods of measurement and computation to determine trajectory data from Askania Cinetheodolite records," NAVORD Report 7907, NOTS 433, U.S. Naval Ordnance Test Station, Inyokern, Calif., Sept. 10, 1951. 3. John Titus and Amy E. Griffin, "A method for the reduction of trajectory data from CZR-1 and RC-2 Bowen ribbon-frame cameras," NAVORD Report 7967, NOTS 537, Naval Ordnance Test Station, Inyokern, Calif., Apr. 30, 1952. 4. Charles T. Lakin, "The 70mm test vehicle recorder," NOTS Technical Memo No. 7740, U.S. Naval Ordnance Test Station, Inyokern, Calif., July 25, 1952. See also: Charles T. Lakin, "The 70mm test vehicle recorder," presented on October 9, 1952, at the Society's Convention at Washington, B.C., and planned for early publication in the Journal. Discussion Dave Miller (Battelle Memorial Institute): I would like to get some confirmation of the apparent fact that your Askania data are correct within one to three feet, is that correct? Mrs. Griffin: Yes. However, this depends on how far it is from the camera to the missile. Mr. Miller: How far? Mrs. Griffin: Within 10 or 15 thousand feet. The random errors in the azimuth and elevation angles measured with Askania cameras at the present time are of the order of one minute. There are also eccentricity errors in these cameras which can be corrected for but they seem to change with time, which makes it difficult to do so. Mr. Miller: I wonder whether you could not release a number of flares with parachutes, so that several of them would always be within the field of view. They should move quite slowly, their motion should be substantially constant, and their motion could be computed, so that the positions of such flares as seen in the photographs could be used as a basis for determining the changes in azimuth and elevation, eliminating the need for dependence on the scales provided on the mounting of the camera. Mrs. Griffin: We, at Inyokern, are right beside the Sierra Nevada Mountains. I don't know whether you have knowledge of the wavefronts there, but this region is where they do their experimental sail-plane flying. The wind velocities are of the order of 60 mph. They may change within 1000 ft and go in the reverse direction. I don't think it is practical. Mr. Miller: Then possibly another site might be considered favorably. 492 December 1952 Journal of the SMPTE Vol. 59