Making Moving Pictures

Progress, Volume VI, Issue 12, 2 October 1911, Page 826

Making Moving Pictures

Probably the highest pinnacle of success to which the photographic art has attained is in the presentation to us of those marvels of modern science known as moving pictures We have all seen the finished result in the Theatres, but probably few realise the immense amount of careful thought and scientific ingenuity which was expended before we enjoyed our evening's pictures. Without going into the "acting" side of the question, which, of course, is a great industry in itself, Ave will endeavour to give some idea of the working of cinematograph machines such as are employed at the principal theatres. Progress is indebted to Mr. Joe Dunn, of the King's Pictures, for the information contained in this article. There are three instruments or machines employed before the pictures are thrown on the screen. All of them embodying the same mechanism and principles,

though each has a function of its own. The first, of course, is the camera, which takes the negatives from which the finished pictures or positives are printed. The sensitised film on which the pictures are taken is contained in a perfectly light-tight magazine with internal gear to permit of the winding and unwinding of the film as required. Another magazine, precisely similar to the first, is provided for the exposed film to wind in, after passing through the camera. The passage of the film through the camera is chronicled on a dial outside, facing the operator, so that he can see at a glance how much is exposed and how many feet of film he has left. The intricate mechanism which takes the pictures, is operated at will by turning a crank. The film apparently passes continuously through the machine, yet there is a distinct pause for each picture to be taken. That is to say, each time the lens is exposed the film is stopped automatically, and it does not pass on again until the lens is covered, otherwise the pictures would be blurred. The pause occupies only an infinitesimal fraction of time, as may. be judged when at the average rate of picture making there are 16 exposures and 16 closures each second. The most common, and perhaps the best lens used is a 3-inch Dallmayer Stigmatic working from P 5 to P 22, sharp at full aperture. It gives simply marvellous results when one considers that the little picture 1 inch by % of an inch enlarges to 30 feet by 26 feet, and shows a perfectly sharp picture, that size at a distance of 140 to 150 feet. The process of development requires great care, owing to the rapid nature of the film, and is carried out in a dark room filled with special tanks for the immersion of the film, which is wound upon frames carrying about 100 feet each. The developer used is from any of the standard formulae for rapid negatives, and when the film is immersed, the operator has to stand by with the bromide to restrain the development should it flash up too quickly. A few seconds delay might spoil the whole film. There are also tanks for washing and fixing, through which the frames go in due course, after which the films are wound on cylindrical slat frames, gelatine outwards, for drying. After drying, the next process is printing, or making the positive which eventually reproduces the picture on the screen. This is performed by a machine which is, in its working, similar to the camera, except that the light is supplied from inside by an 8 c.p. 100 volt Osram light, which is adjustable to suit the varying intensity of the negative film. This requires great attention, and the operator watches it critically as he turns the handle. No lens is used in this process, the negative and the blank film, which is to form the positive when developed, being both passed by the same set of cogs and claws and pressed closely together, over the aperture from which the light is passed, through the negative on to the positive film. The same ingenious arrangement as in the camera permits of movement of the film only when the light aperture is closed, and automatically locks the film in place while the light is exposed. The positive film is rolled on racks and eloped in the same way as the negative, except that it is a much slower pro-

eess, being about the same speed as ordinary Ilford plates. Any bromide formula is used. The tanks for developing and fixing usually hold about 4 gallons of their respective solutions, which is sufficient to treat 100 feet of film at a time. They are usually maintained at a uniform temperature of 70° Fahrenheit to get the best results. The positives are dried in the same manner as the negatives, and when dry are carefully scrutinised for defects. A defective picture can be cut out and the film joined invisibly with a, special cement prepared for the purpose. The third machine, the lantern or re-

the right focal length behind the double lens condenser, which gathers in the rays and concentrates them so that they are applied to the film at approximately 60,000 candle power. The heat at this concentration point is also intense and would fire the film if it were exposed to such heat for even a second of time. To obviate this risk of fire, and it is a very serious risk, for the film is highly inflammable, an ingenious contrivance has been devised, whereby a steel shutter, backed with asbestos, interposes itself automatically between the light and the film every'time the machine stops. The same intervals are observed in reproduc-

producer, is more complicated than either of the others, inasmuch as in addition to the mechanism for driving the film it contains the electric Arc light, and condenser, and the lens. The light is supplied by a 60 volt continuous current to a name are of 12,000 candle power. The carbon pencils are Gin long, and are almost used up at the end of an ordinary evening's run. The lantern in which the arc burns is of sheet steel, and has to stand considerable heat, as may be imagined when it is said that between the points of the carbon pencils the heat is 2000° Fahrenheit. A piece of steel, such as a knife blade, fuses immediately and drips away on being introduced between the points. The are light, as mentioned above, is of 12,000 candle power, and is situated at

ing as with the camera, i.e., 16 exposures and .16 closures per second. Beyond the film is the Darlot lens, which magnifies the picture and projects it on the screen.