American cinematographer (Jan-Dec 1924)

July, 1924 AMERICAN CINEMATOGRAPHER Nine Cine Camera Taking 3200 Pictures Per Minute Progress in Sending Motion Pictures by Radio From Transactions, Society of Motion Picture Engineers By C. Francis Jenkins Inventor Gives Information on His Latest Creations. PERHAPS the progress which has been made in the perfection of the high speed camera which the writer brought to the attention of the Society at the Buffalo Meeting, October, 1921, might be interesting to you as engineers, as it points out the unique character of the instrument now available for the study of unusually high speed motions. Pictures are now regularly made at the rate of 3200 photographs per second, that is, 200 times standard (16 pictures per second) motion picture speed. In the study of high speed motion it is comparable to a microscope of 200 diameter power in the study of small objects. Speeds still higher are believed feasible, but perhaps not often required. No radical modifications in the camera have been made in the past two years in order to regularly attain this high speed. The lens carrier now contains 48 matched lenses. This matching we had to do ourselves after the lenses were received from the manufacturers. It is a tedious job, but can be done if one is patient and resourceful. The other difficult problem was mounting them so as to get absolutely steady pictures on the screen when prints were made from the negatives. No machine shop tool was found which gave the requisite degree of accuracy, so a special method had to be worked out therefor. The camera has been made very rugged, and is driven with a battery motor which permits carrying the camera into the field beyond the reach of city power current. We still continue to employ a loop in the film to insure flatness at the picture exposure aperture. Friction tension is absolutely out of the question. It has been found necessary to continue the lubrication of the film, but this is easily and automatically done by the use of a small paraffine block, and requires no attention. Subjects for study of which this camera is particularly adapted will readily suggest themselves to you. The subjects we have already photographed range from simple to more complex ones. Most of the surprises have been found in the simplest subjects. In photographing a little girl skipping a rope, it was discovered that the loop end of the rope after it dragged under her feet accelerated much faster than any other part of the rope, so that the loop end actually reached a vertical position above her head well in advance of any other part of the rope. No plausible explanation of this has yet been proposed by any of those who have seen these pictures. The test film made of the airplane propeller turning over 1600 R.P.M (wholly invisible to the eye, of course) was the subject that sold one of these cameras to the Air Service of a foreign nation. Perhaps the most interesting subject was the photographing (at 3200 exposures per second) of pigeons wings when the pigeons were released from a basket. It is a classic. The wings touch both above and below the body (Continued on page 19) SINCE the presentation at the Atlantic City Meeting of the methods and apparatus employed in the transmission and reception of photographic images by radio, development has progressed quite satisfactorily. The quality of the reception has been raised, while the time required for the transmission of photographs has been reduced to less than a minute. This higher degree in the quality of the picture has come from the adoption of a special lamp, made available through the belief in our ultimate success by the president of the Society of Motion Picture Engineers, Mr. L. C. Porter, for he had the lamps made for us by the General Electric Company, Harrison Lamp Works, and I feel that he believes his confidence has been justified. A hundred lines per inch has been found quite sufficient for all classes of pictures; and fifty lines per inch adequate for most. By judicious selection of the lamp and its careful location, and the adjustment of other associate parts of the radio camera, a very satisfactory 50-line portrait can be obtained in less than half the time required by the 100-line setting. Radio Photo Messages The speed of message transmission by this same radiophoto process is about ten seconds per message. When a special lamp, now being developed, is available, it is believed a complete 100-word message can be sent every second. The messages will be put on a long, rather wide band, in a series of 25 messages to each band, and this moved through the sending machine, in such fashion that one complete message is sent every second. A photo-paper band at the receiving end will be provided, and synchronously moved one step every second. Upon this band the 25-group of messages will be photographed. Japanese Characters by Radio In this connection it might be mentioned that, for the first time in history, Chinese and Japanese messages in native characters can be transmitted by radio. Military officers stationed at the Japanese Embassy in Washington express their belief in the great value of this method for official communication by their government. Radio Vision Speeding up the apparatus to 16 pictures per second has given us radio vision, as a laboratory demonstration, although the few lines per inch so far attempted give us but a crude picture, a picture which is unmistakable, however. The present method of getting the necessary speed is by mounting a series of lenses on the back of a prismatic ring. To attain the necessary speed in simpler mechanism we are making the prismatic ring in four section to be used without the multiple lenses. This gives us twice as many lines per inch as when a double prism ring is used, and four times as many lines as with a single prism ring. I think still more prisms to each ring can be made, but this has not yet been undertaken. (Continued on page 18)