Projection engineering (Sept 1929-Nov 1930)

Projection Engineering, April, 1930 Page 29 A NEW PORTABLE LIGHT INTENSITY METER J. L. McCoy'' ANEW light intensity meter has been developed to take advantage of the many desirable features of the photoelectric cell. With this meter, the intensity of the light at the point of test is indicated directly on a scale without the necessity of balancing against a standard comparison lamp. The meter is a complete unit, carried in one case. The light sensitive pick up is a photoelectric cell covered with a shield, in the side of which a window is cut to admit the light to be measured. The photoelectric cell unit is connected to the meter by a 6-ft. cord, making it possible to move the cell anywhere within that radius without moving the meter case. The instrument contains a commercial, portable microammeter which is calibrated directly in terms of foot-candles. The energy required to operate the meter is furnished by the smallest size of "B" batteries mounted in the case, and the current consumed is so small as to be almost negligible. The life of the batteries in service is practically the same as their shelf life. The photoelectric cell is somewhat similar in appearance to a radio tube and contains two essential parts, — an anode and a cathode. It is the cathode coated with light sensitive material that gives the tube its characteristics. There are a number of different types of photoelectric cells and their characteristics vary materially with the elements used for the cathodes. They can be made of different materials to respond to different wavelengths of light. One type of cell is in use which responds only to light of wavelengths beyond the visible spectrum in the ultra violet region. The cell used in the light intensity meter is a special one having a very broad response, covering the visible spectrum. When used in motion-picture studios to measure the intensity of the illumination on the "sets," it is found that the response curve of the cell closely approaches the sensitivity of panchromatic film in combination with the light from Mazda lamps. The meter thereby enables the cameraman to determine definitely whether the illumination is sufficient for good photography. * Vacuum Device Department, Westinghouse Lamp Company. FIRST STATION WITH SLOW AND FAST TURNTABLE RECORDER The Milwaukee Journal station, WTMJ, has recently installed the new Western Electric double 78 and 33 lA r.p.m. turntables for electrical transcription. It is the first station in the country to be so equipped, with turntables for both the slow and the fast recordings. But it will not remain alone in the field for long. Other stations are recognizing not only the benefit to be derived from the use of recorded programs, but the absolute need for them if the station is to broadcast the finest available material. Of course, turntables for recorded broadcasting have been in existence before now. But many of them have been inferior in quality. With the new Western Electric equipment inadequate phonograph pickups, distortion, and varying tonal qualities will be replaced by unfailing fidelity in reproduction. The installation of proper turntable and transmission equipment by broadcasting stations is a great forward step in recording presentations. But a recorded program is no better than its preparation and recording. With the acceptance and installation of more than adequate equipment at the broadcasting end, it only remains for programs to be prepared and recorded in a manner befitting the fine machinery for their broadcasting. Radio program sponsors, to take the fullest advantage of the new recorded program facilities of the radio stations, should see to it that programs worthy of this widespread broadcasting are prepared by the finest organization available and recorded by those who know their business and have recording facilities that are on a par with the finest turntables now being installed in the broadcasting studios. Sound Studios of New York, Inc., is carrying on a campaign against the preparation and recording of programs by concerns on unlicensed equipment, whose work is of such poor quality as to transform their clients not only into enemies of recorded programs in general, but also of radio as an advertising medium. The radio stations that are installing the latest recording turntables and pickups should now accept for broadcasting from their fine equipment only such programs as are well prepared and recorded on apparatus of as high a quality as their own. TELEVISION SIGNALS TRANSMITTED TWENTY THOUSAND MILES A TELEVISION picture which had traveled approximately twenty thousand miles through space was received with a fair degree of accuracy in the radio research laboratory of the General Electric Company on the morning of February IS, establishing a record for television reception. The picture, a rectangular design in black on a white card, was transmitted by the General Electric short-wave station, W2XAF (31.48 meters) Schenectady, N. Y., received in Sydney, Australia, by station VK2ME, rebroadcast by that station (28.8 meters), and received back in Schenectady in about an eighth of a second. Both the transmission and reception took place in the laboratory of Dr. E. F. W. Alexanderson, which was connected by wires to the super-power transmitter at South Schenectady and the experi mental receiving station at Glenville, a few miles from Schenectady. "Considering the fact that the picture bounded through the ether ripples twice over so great a distance, I am very much enthused with the results of the experiment," Dr. Alexanderson said. "I really did not believe the picture would be sufficiently distinct to tell what it was because so many conditions existed to upset matters. There are ripples in the ether such as there might be in a pail of water. When you look into a pail of water having a rippled surface, the reflected image of anything is indistinct, the lines of the picture being exaggerated and somewhat fuzzy. In this television rebroadcast it was much the same as though this image seen in one pail of rippled water had been reflected in still another pail of rippled water, corresponding to the rebroadcast back from Australia. Naturally there would be considerable distortion, and I was very much pleased when I saw that this double distortion did not entirely wipe out the image. The experiment was carried on for about five minutes, and many times during this period the lines of the rectangle were distinct enough for observers to distinguish the picture which was being broadcast." No effort was made during the experiment to send a picture of persons. The time was short, and only the painted rectangle was used. However, Dr. Alexanderson intends to carry on with further experiments in long distance television transmission and reception. ▲ THE PSYCHOLOGY OF SOUNDS IN SCREEN PRESENTATIONS (Concluded from page 21) was simple and effective. Sound pictures will find a way to meet this requirement and still have what is portrayed on the screen appear logical. Resonance Background Missing All of the looked-for background, such as auditorium or room resonance effects sensed where the listener hears orchestras,, bands or choruses actually playing and singing, are so far missing in sound picture reproduction, but in time the remedy will be applied. Children's voices, too, have a far away sound accompanied by "lisping" or other natural sounds, caught by the pickup system and reproduced through the present loudspeakers, but which heard directly are rejected by the ear. The nearly two hundred members of the S. M. P. E., who listened to Dr. Pitkin's talk took away with them a new and broader conception of what is before them in the way of development. Every man present seemed to sense that he was listening to the unfoldment of a new and alluring prospectus of the talking picture of the future.