The Cine Technician (1943 - 1945)

82 T II i: • I \ K T E i HNIi 1 \ \ S< pti mb< r 0< tober, 1944 Edited by A. E. Jeakins Technical Abstracts A Direct Reading Audio-Frequency Meter (S.M.P.E. Abstract in International Photographer, May, 1944). This is an instrument capable of indicating audio-frequencies of 1<i to 50,000 cycles to accuracies limited only 1>\ the panel meter or pen and ink chart recording meters. Source of audio-frequency voltage is fed into a high impedance grid circuit and due to plate saturation of electron discharge tube the incoming wave shape is changed to a square wave which retains the original frequency but is not affected by variations in signal voltage amplitudes. Only one volt is necessary to trigger the grid circuit. Output of first tube is amplified by a direct coupled multi-vibrator circuit, consisting of two tubes whose circuit constants have no resonant i ffects on above frequencies. Wave shape remains unchanged and amplification is constant. Appropriately chosen capacitive and resistive networks then permit the integrated pulses to collect on the grid of the counter-tube circuit. To produce a linear frequency calibration, the grid circuit of the counter-tube is biased to plate current cut-off with zero signal input A 5 Ma milliameter in the plate circuit serves as a pulse counting device, and provisions are made to use an external recorder. Gas-discharge tubes employed in the B voltage supply serve to stabilize operation from 105 to L25 volts with less than 3% full scale change in frequency indication. A plate overload relay is used to protecd the panel meter, should frequencies applied to input circuit be greater than those for which the selector switch is set. An overload pilot lamp is mounted mi the front panel. Thomascoior (Alvin Wyckoff, American Cinemato grapher, May, 1044). This colour system, named after its inventor, Richard Thomas, employs standard black and white technique and developing methods. The special optical unit which takes the place of the normal camera lens produces four colour separation negatives within the limits of a single frame at each opening of the shutter. The unit is available in various focal lengths. Bight is admitted i rough a single aperture and is carried fco the film plane by means of refraction and partial and total reflection. After passing through the filters t he images are of equal delisit \ . The projection print is a black and white positive, each frame of which carries lour images. The light from each image passes through a Thomascolor projecting unit, which incorporates colour filters, and which superimposes the tour images in registei on the screen. It is claimed that the sen en can be approached to within arm's lei ; without fringing or loss of definition being e\ ident. The negative is developed like any ordinary black and white film. A> all the images are on the same strip they are developed simultaneoush and shrinkage is equal throughout. Printing foil normal black and white technique. Xo special equipment or chemicals are ecessary\ The Weston calibration for exposure is rated 1^ stops higher than for black and white. With coated lenses opening up one stop is sufficient. The Thomascoior photographing unit is a ■ _ assembly without any moving parts. It takes the place of the lens in all standard still and motion picture cameras. The projection unit wine1 about the size of a standard projection lens equally simple to fit to any projector. Thon color can be applied to still photography as well as motion pictures and colour prints on paper can be made from the Thomascoior separation negate. Art Reeves Reflex Camera i If. Boyce, International Photographer, April, 1944). An interesting feature of this new camera (not available for civilian use till after the war is I finder which allows the cameraman to see exactly what he is photographing through the same lens that is exposing the film. The camera lias been designed to work satisfactorily at both high and low temperatures to meet the requirements U.S. Army Air Force. Under test it has worked well at 160° above and 70° below zero. All c: stings are made of aluminium, anodized to protect them against the action of salt water. Other tures are variable shutter control 170° to dowhich can be operated while the camera is running; lightweight motor 111. -Jl and 48 fr: n second: various models to run on 16, 24 or 110 volts; three-lens turret. Bens mounts have sunshades which take filters fitting close to the lens. Magazines are made with revolving di>c> in t up compartments. This prevents buckling w film rubs against the side of the magazine w the camera has to work lying on it di 1 in^ microsc< >pe is adjustable to operator's e\ e. Pi* iiir' is magnified righi side up and right w;o round. An auxiliary frame finder is permanently sel above the micro-cop,, tor emergency use. Tin ret',, ting element in the finder optical system lie \ aried lor two difh rent light conditions, [n position it passes ."ill" of the light to the till: therein cutting the Light one lens stop. The balance of the light passes to the finder. In the ol position if passes about 95% of the light to the film and normal stops can be used.