The Cine Technician (1953-1956)

nil CINE TECHNICIAN November 1956 A Technician's Notebook XEROGRAPHY rPHE Rank Organisation have 1 announced that they are joining with the Haloid Company, U.S.A., to form a company here with an authorised capital of £1,200,000. The new company will be known as Rank-Xerox Ltd.; it will manufacture and market equipment and supplies for a new electro-photographic process which does not use conventional sensitised materials but produces the finished print on ordinary paper. What is this process, which goes under the name of Xerography? According to an editorial in the B.J., which refers to a lecture on this process, or rather the R.C.A. development of it known as Electrofax, given at the Royal Society of Arts, it is an electrostatic process for graphic reproduction and photography, depending on the use of a photo-conductive insulating material the surface of which can be electrically charged. Development after exposure is by dusting the plate with a very fine powder and prints are made by transferring and fixing the powder image to a paper or other base. Inexpensive Material In the Electrofax process the photosensitive element is a mixture of a photosensitive photo-conductor (very fine and pure zinc oxide) in a resin binder. This mixture can be coated on practically any base, metallic or otherwise, and is particularly used on an ordinary paper base when it provides a coated material which possesses the general characteristics of a normal silver halide printing (taper. The material is inexpensive, and insensitive to light until it is electronically charged, a simple operation carried out in the dark or in suitable safelight conditions, and involves a transfer of ions by a charged win' being swept across the coated surface of the paper. In this charged state the paper is ready for exposure, which can be made by any of the usual methods and has the effect of reducing the electrostatic charge in proportion to the amount of light falling on the coating, leaving a latent electrostatic image on the surface of the coating. This image can be developed by applying a positive charged pigmented resin powder, or toner, which adheres by electrostatic attraction to the negatively charged areas on the coated surface. The ' toner ' can be charged and applied in a number of ways, one By A. E. JEAK1NS of which is by using a magnetic brush. This consists of a permanent magnet which carries at one end a mass of iron powder loaded with a fusible toner powder. In this way an image on paper or other base is built up by deposits of the toner and is capable of a wide control. Fixing of the image is simply accomplished by baking for a few seconds at a temperature which will cause the toner to melt and fuse to the paper surface. It seems that the present applications of this process are mainly concerned with making microfilm copies, engineering drawings, recording data from cathode ray tubes and other such commercial uses; but, as the B.J. editorial concludes, ". . . there are unlimited possibilities that may well provide us with solutions of many of our problems of today — may in fact open to us entirely new conceptions of photographic reactions . . " Mention of the B.J. (British Journal of Photography — in case anyone doesn't know! ) reminds us to offer belated congratulations to our respected and very senior contemporary on its attractive typographical ' new look ' which it assumed in August. The General Electric Company of America announce a new exposure meter having twice the sensitivity of its predecessors. Named the Guardian, it has a light multiplying attachment which increases the meter's sensitivity sixty-four times for incident light readings and four times for reflected light readings. The time-lapse technique of photography used to compress phenomena occupying hours or days such as the growth of plants into a few seconds or minutes has now been applied to time-andmotion studies. " Memomotion ", as this technique is called, was developed in 1948 at Purdue University in U.S.A. by Dr. Marvin Mundel and Professor Wallace J. Richardson. The Du Pont Company are responsible for supplying the information which follows. In contrast with time-and-motion studies which involve continuous cinematography, with many exposures a second, which produces the effect of slowing down the operation to be studied, " Memomotion " uses intermittent exposures to condense the action, and allow projection of the film either at normal speed, or frame by frame. A condensed photographic memorandum is obtained by placing a motion-picture camera at a key point, and exposing the film at intervals ranging from one frame every twenty minutes to one per second, depending on the procedure to be studied. Rapid Visual Analysis The technique emphasises important steps rather than details of the process under study, permits its rapid visual analysis, and is more economical in film than continuous or high-speed cinematography. An hour-long operation can be reviewed in less than four minutes, and a 15-minute film can represent more than four hours of elapsed time. Equipment used by Du Pont engineers in their " Memomotion " units includes a 16mm. cine camera with a 100-ft. capacity fitted with 13mm., 25mm. and 102mm. lenses; a timer control box equipped with a solenoid mounting for the 16mm. camera; and an ■inalysis projector with hand crank and frame counter. Availability nowadays of very fast film emulsions allows a " Memomotion " unit to operate without special lighting.