International photographer (Jan-Dec 1935)

Thirty-two The INTERNATIONAL PHOTOGRAPHER Max. 19S> MOTION PICTURE (Continued inch) in thickness separates the diaphragm on one side from a flat metal plate called the damping plate. The diaphragm is clamped between stretching rings that are screwed up after assembly until the diaphragm is drawn so tightly that its resonant frequency is in the neighborhood of 5700 cycles per second (c.p.s. ). This places the natural period of the diaphragm safely out of the normal frequency range of the human voice; although from a sound transmission standpoint it would be better to have the resonant point well about 8000 c.p.s. The diaphragm being mounted so close to the back plate provides a high damping effect and tends to reduce the sensitiveness of the transmitter ; but the stretching of the diaphragm and the presence of the back plate help to reduce the effect of diaphragm resonance and improve the fidelity of reproduction obtained with the microphone. The Carbon Cells On each side frame opposite the center of the diaphragm are mounted carbon electrodes similar to the ones employed in the single-button carbon microphone. Opposite these electrodes are pure 24-karat gold-plated areas on the diaphragm ; and the two chambers formed SOUND RECORDING from Page 9) between the carbon electrodes and gold-plated spots on the diaphragm are filled with polished carbon granules. These cells are each designed to have a resistance of 100 ohms, as measured from the carbon electrode to the diaphragm, thus providing an over all resistance of 200 ohms from one carbon electrode to the other. This over all value is said to be the operating resistance of the microphone; so the microphone will work most efficiently into a circuit having an impedance of 200 ohms. The arrangement of the carbon cells and the associated circuit may be seen schematically in Figure 2. In this diagram, the transmitter is connected to a standard microphone transformer that has a primary impedance of 200 ohms and a secondary that is of the proper impedance to work into the grid-filament circuit of a vacuum tube. A potentiometer for regulating the amount of current supplied to the buttons of the transmitter by the battery, and jacks to permit the plugging in of a milliammeter to read the current drawn by each of the buttons, are also shown. This is the standard arrangement used with the microphone in public address systems, with the microphone in public address systems. * * Figures No. 1 and 2 mentioned here will be shown with Chapter XIX in June issue. California Pacific International Exposition Camera ! Lights ! Action ! ! Sink 1 1 1 The curtain rises May 29th on America's Exposition, 1935 in world-famous Balboa Park, San Diego. Of interest to photographers throughout the world is the extensive Fifth Annual International Salon of Photography to which internationally known lens experts — as well as hundreds of lesser lights — have sent prints will open simultaneously and run for the duration of the Exposition— until Nov. 11th. The salon will be housed in the new, modern Palace of Photography in the heart of the Exposition grounds ; here, too, will be found the office, studios and dark-rooms of John Sirigo, official photographer to the Exposition. Stand in the jeweled tower of the Palace of Science in Balboa Park and lift your eyes to the glittering shore-line of the blue Pacific. There you may see, mile on mile, the snowy froth of the surf-line as it breaks incessantly on the quiet sand of the beach. From this lofty vantage point it is not difficult to visualize those first proud Spanish ships that sailed up from the Southern horizon almost 400 years ago. They were odd ships, with their round bows, their square sterns and towering poop decks lifted to the sky. And yet they had about them a certain grandeur that does not attach to the liner of today. There was paint and gold, carving and armorial emblazonry about them that somehow suggested those proud, impoverished Spanish gentlemen in command. Drop your eyes to a nearer scene and drink of the beauty that is part and portion of this modern San Diego. Here, you will say, is the city of your dreams — here is a city sparkling like a rose diamond in its setting of green, and sheltering easily in the thirteen-mile stretch of its bay more than half the grey vessels of the American fleet. The gem city itself is built around Balboa Park, third largest in America, where an abundance of foliage gleams in perpetual sunshine. Framing the scene, but dim in blue distance, are the high green peaks of the distant Cuvamacas. This, then, is the setting — this is the background against which will be woven the colorful tapestry that will be America's Exposition — 1935. From the vantage poinc of this commanding Tower, one looks down upon the trail-slashed timber lots and gardens of 1400-acre Balboa Park. Nearer at hand, clustered about the base of this high place, one sees the tremendous unit of artistic buildings in which will be housed the varied exhibits of this California Pacific International Exposition. Here, on May 29, 1935, the people of California's first city will present an exposition that promises to be unrivaled in the annals of west coast history. In this sub-tropical garden of the southland, housed in buildings seemingly rich with age, the countless exhibits of a changing world will be offered with the spice of contrast. San Diego builds for this Exposition with the priceless background of careful preparation. Over a period of years in which Balboa Park has been developed to the point of perfection, the people of the city have had in mind the ultimate presentation of an international Exposition. Millions have been poured into this plan and many of the Spanish structures in the exhibit unit have the advantage of a floral and shrubbery back-drop sufficiently mature and mellowed as to have moulded themselves into the very lines of the colorful buildings. There is nothing of rawness in this San Diego Exposition. High towers — architectural triumphs in themselves, are made more beautiful in the blaze of bougainvillea climbing to their highest point. Cream white facades half revealed through the drooping calm of pepper trees ; bell towers lifting high above the heads of tropical palms and overshadowed in turn by the broad-leafed fragrance of eucalypti. The California Pacific International Exposition has for its setting a background of shrubbery and floral decoration conceived in the slow, deliberate process of nature. An amazing variety of shrubs and flowers — incredible reaches of timber where tropical palm and silver pine interlace their branches — calm, restful courts — shadowsplashed patios — lily pools reflecting the red-tiled roofs of overhanging buildings, these things are part and portion of an exposition setting that no spot on earth could duplicate. Man's achievements will be graphically depicted in every conceivable form. Exhibits of commerce and indus Please mention The International Photographer when corresponding with advertisers.