The international photographer (Jan-Dec 1941)

be vibrating. The microphone has as its purpose to change into electrical vibrations in the wires leading from it. the mechanical vibrations of the sound waves, and does this by causing a large amount I relatively ) of current to flow through it when a condensation happens to be hitting it, and a small amount of current when a rarefaction follows. Thus, the electrical output of the microphone will be a series of changes from large current flow to small current flow, which will be an exact replica of the condensations and rarefactions hitting the microphone, and this, in a complex form of varying intensities, frequencies ( or speeds), and patterns, will represent the complex and interwoven nature of familiar sounds, as of an orchestra. But the electrical output of so sensitive a device as a microphone is extremely weak, and before it can be made to do any work in the recorder it must be built up to proportions strong enough to do so. This is the work of an amplifier, which simply changes the microscopically minute impulses coming from the microphone into strong electrical currents, measurable, and capable of doing mechanical work. Skipping all the refinements of present day recording apparatus (such as attenuators, compensators, mixers, etc.) the output of the amplifier then comes to the recorder proper. Of these, there are two basic types. In one system, the RCA, the intensity of the light remains constant, and hence the density of the track is always the same; but the width of the track will vary. This is accomplished by focusing a light (called an "exciter lamp") through a mirror — a moveable mirror, which is attached to an instrument called a galvanometer, which is a highly specialized form of an electromagnet. When a strong current is sent through this magnet, or galvanometer, it will pull the mirror into a position which will expose the entire width of the sound track on the film. When a weak current flows it will permit a spring to pull the mirror into a position where the reflection of the exciter lamp will only cover a very small portion of the track and expose only the small portion. Now, then, with the film running through the recorder, the movements of this mirror causing alternate wide exposure lines and narrow ones — corresponding to the vibrating electrical impulses coming from the microphone, and which represent the sound waves, will expose the photographic film, giving it an impression (photographic) of what is happening in the galvanometer, and consequently, in the microphone. And, when this film is developed, we see the characteristic hills and valleys that represent the sound itself. In the Western Electric system, the width of the track is constant. Instead of having a galvanometer which moves a mirror, we have a "light valve," which permits a lot of light to pass through it when a strong current is flowing, and a small amount of light when the current is weak. The result is a track which is of uniform width, but of a varying density. But the variations in the amount of light that can pass through a small slit — or line — of light focused on this film are the same. They are merelv expressed in different terms. The reproduction of this track is just the reverse of the recording. A small beam of light from an exciter lamp is focused on the track, behind which is a photoelectric cell, which is sensitive to light changes. Where a condensation occurred in the sound wave, a strong current was set up by the microphone, which caused a dense exposure on the film. When this was printed on the positive it became a light exposure, or line, and this now is permitting a lot of light from the exciter lamp to reach the photocell. The opposite is true for the instant there is a rarefaction. The photocell, then permits varying amounts of electric current to pass through it, varying in the exact manner in which the microphone picked them up in the recorder. This output, too, is very small, and is passed on to an amplifier, which builds it up to the point where it is strong enough to do some practical work, and is then passed on to the loudspeaker, where the electrical impulses — or vibrations — are turned back into mechanical movements — or sound waves. P fl T € n T s By ROBERT W. FULWIDER, Patent Attorney, Los Angeles No. 2,258,187— Integral Mask for Multicolor Film. Leopold D. Mannes, Leopold Godowsky, Jr., and Lot S. Wilder, assignors to Eastman Kodak Co. Application May 15, 1941. In Great Britain January 15, 1940. 4 claims. A color film for producing corrected color prints which has in order: a blue sensitive emulsion; a yellow filter; a slow blue sensitive emulsion ; and green and red sensitive emulsions; of which the slow blue sensitive emulsion is developed to form a metallic silver masking image. No. 2,258,313— Film Filter. Joseph M. Bing. New York. Application February 12, 1941. 5 claims. A film scraper having a guide rod carrying a slidable head which may be moved along the rod and across the film. No. 2,258,356— Film Splicer. Jacob M. Goldberg. Denver Colorado. Application March 18, 1940. 12 claims. A power operated film scraper in which an electric motor drives a toothed cutter which may be manually moved across the film. No. 2,258,558 — Apparatus for Obtaining Photographs in Color by Projection Copying. Anne Henri Jacques de Lassus Saint Genies, Versailles, France. Application March 10, 1939, Ser. 261,066. In France March 18, 1938. 5 claims. A device for projection copying of an original film bearing a plurality of separation records onto a copy film provided with a plurality of sensitized layers having different photographic properties. No. 2,258,976 - Photographic Sound Track. Le Roy M. Bearing, assignor to Eastman Kodak Co. Application May 3, 1940. 4 claims. The method of producing a sound track in a photographic film, which comprises printing the sound track image on the film, developing the film to a negative sound image, and treating the sound track area of the film with a combined sulfiding and iodizing bath to form a combined silver sulfide and silver iodide sound track in the film. No. 2,259,415 — Camera Focusing Device. William C. Eddy, Kenilworth, 111, assignor to Balaban & Katz Corp., Chicago, a corp. of Delaware. Application February 5, 1941. 5 claims. A camera focusing device in which rough focusing is done by a lever moving in a plane parallel to the optical axis of the lens, and screw means mounted on the lever for effecting precise focusing. No. 2,259,493 — Automatic Film Jam Shutoff. Melvin Shorr, Dayton, Ohio. Application April 4, 1941. 5 claims. A motor driven film rewind with a loop catcher which, if the film does not remain taut, turns off the motor power and signals the operator. No. 2,260,092 — Method of Creating Cartoon Effects. Leonard B. Pickley, assignor to Walt Disney Productions. Application Dec. 26, 1939. 2 claims. A method of producing shadow effects in animated cartoons by placing a colored transparent film over the picture to be photographed, applying a protective coating over parts of the transparent film, removing the color from the remaining parts, and then photographing the whole. International Photographer for December, 1941 21