International photographer (Jan-Dec 1934)

December, WM Th INTERNATIONAL PHOTO Q KAI'HER Twenty-one the same relative aperture, and consequently the same speed and the same exposure time with all lenses. Depth of focus being in inverse proportion to diameter of aperture and therefore directly proportionate to the ratio number, it follows that, 1 — With the same lens, or with several lenses of the same focal length, depth of focus with the various apertures is directly proportionate to the ratio numbers. 2 — With the same ratio number (relative aperture) and the same focal length, depth of focus as well as speed is the same. The apertures which are marked have been so chosen that each succeeding smaller one has one-half the area of the preceeding larger one, and consequently requires double the exposure. Beginning with f/1, an aperture, the diameter of which is equal to the focal length of the lens, the series of apertures will be as follows: f/1, f/1. 41, f/2, f/2.83, f/4, f/5.6, f/8, f/1 1.3, f/16, f/22.6, f/32, f/45.25, f/64, f/90.5. The Uniform System (U. S.) is based on the focal ratio system as shown in the following table, and the aperture numbers give directly the relative exposures: Relative Aperture — f/1 1.3 f/4 U.S. No. 1 f/5.6 2 f/8 f/16 f/22.6 f/32 16 32 64 f/64 f/90.5 256 512 f/45.25 U. S. No. 128 An aperture of f/4 is here taken as requiring a unit exposure and is marked 1. The next smaller opening, f/5.6, requiring double the exposure of f/4, is marked 2 ; the next one, f/8, requiring double the exposure of f/5.6 and four times the exposure of f/4, is marked 4, and so on. The numbers 1, 2, 4, etc., thus have reference only to the comparative exposures, and the exposures read directly as those numbers. If No. 1 requires 1 second, No. 16 requires 16 seconds. If No. 8 requires 3 seconds, No. 32 requires 12 seconds. If No. 128 requires 2 seconds, No. 16 requires 1/4 second, and so on. The necessity for faster lenses has been recognized for more than sixty years. It was not until 1881 that Dr. Schott and Prof. Abbe discovered that it was possible to produce a glass with a refractive index as high as heavy Hint, but with no more dispersion than ordinary crown glass. And it was from such glass that the first anastigmat was made in 1890. This lens had astigmatic correction over a large flat field and at the same time spherical correction for a large opening. Cinematography, of course, brought an even more intense need for faster lenses. It was for this reason that Bausch & Lomb began certain experiments in 1925, under the direction of Dr. W. B. Rayton, to develop a new glass for a new lens capable of giving the best possible definition over the entire area of the picture with the highest speed consistent with a reasonable depth of focus. The speed adopted, f/2. 3, has become more or less standardized as the best compromise between illumination and depth of focus. The definition and covering power of the new Raytar lens, however, is comparable with the results obtainable heretofore only with much slower lenses. This characteristic makes the lens a very flexible tool in the hands of a skilled operator. He can make pictures as sharp as he likes or he can introduce whatever degree of diffusion he prefers. Contrary to all precedent, the various focal lengths are not geometrically similar. Motion picture photography differs from ordinary photography in that regardless of the focal length of the lens used, the picture area is constant in size so that the angular field of view decreases progressively as the focal length is increased. Taking advantage of this fact, simpler constructions have been introduced in the longer focal lengths of the Raytar, gaining thereby a very desirable reduction in weight. For instance, the simplification of construction in the case of the 152 m/m focus lens is such as to justify reducing the relative aperture to f/2. 7 whereby we gain a significant reduction in bulk. The lens is fully corrected and will perform equally well with arc or incandescent illumination, and with orthochromatic, panchromatic or high speed film, taking equally sharp pictures of any color or color combinations. OUR CAMERAMAN IN LITTLE AMERICA RADIOS US MACKAY RADIO RADIOGRAM November 21, 1934. Byrd Expedition Little America via San Francisco, California. Herbert Aller, International Photographers, Local 659, Hollywood, California. Would appreciate you insert following in December number International Photographer if in time stop Sincerely wish every member of the International Alliance a very Merry Christmas and Prosperous New Year. Sorry am unable to send individual radios. Kindest regards. John L. Herrmann, Local 659. Mr. Aller replied to this and Mr. Herrmann answered as follows: Many thanks your radio stop summer with us again temperature around zero almost too warm for comfort stop have been running the Paramount Penguin Theatre for past year using Western Electric Sound Projector and our two snow vaults contained ninety-seven programs stop have run pictures from one to five times each ; musicals have greatest number of runs stop hope to see you and the boys next year best wishes. JOHN L. HERRMANN. Max Factor's MAKE-UP A, Easy to Apply Easy to Remove ^ Stays on All Day Photographically Correct MAX FACTOR'S MAKE-UP STUDIO • HOLLYWOOD Please mention The International Photographer when corresponding with advertisers.