Amateur Cine World (February 1937)

Lhe COLOUR SEPARATION PROCESS (Continued from previous page) the so-called “‘floating,’’ the spectator getting the impression that the actor is in place all right, but that in some way he does not fit into his surroundings. Above all, you must make a number of experiments to find the right lens stop. Focussing will also need additional care at large apertures as the presence of the red-toned positive in front of the sensitive film must be allowed for. This method is not for the beginner, but the serious worker is sure to find a very interesting field for experiments in these lines. Change also the colour of your blue background if the effect is not satisfactory at once. Two practical problems must now be solved. First, how to tone the background film into red. Put the background positive into a simple acid hypo-bath for about Io minutes and then wash it thoroughly for half an hour in running water. Afterwards prepare a bath consisting of 20 grammes of potassium-ferricyanide for one litre of water. In this solution the black silverimage disappears entirely. Leave the film in this bath for about five minutes and wash it afterwards until the yellow shade is gone. This may last about 10 minutes. After this the film is put into a toning bath composed of 50 grammes of copper-chloride in one litre of water. The film takes on a light red shade in this and after proper washing and drying is ready to use. All these operations can be made by ordinary daylight. As the film is a little intensified in this bath, it is advisable to take a rather transparent original positive for the background. When you have completed your preliminary experiments never charge the camera with more film than you intend to use for that one particular colour separation scene. I make it a rule never to load more than 9-12 feet —sufficient for one trick shot. There are three methods of inserting both films into the threading and the gate. If the background is one of continuous motion, make up two rolls of film, one being the raw film and the other the toned background. As you have only about 9 feet from both, you will have ample space in the upper part of the camera to place both film rolls one beside the other. On the sprocket wheel you unite the two stocks and form the loops in the usual way, but taking care that the outer film is just one frame longer to form the loop. In the gate the films pass in close contact and the lower loop should again have one frame more for the outer film strip. At the take-up the films run together upon the same reel or camera-kernel, as the case may be. In cameras where no loop-forming is necessary (as with a number of 9.5mm. cameras) the proceeding is the same, only the loops being missing. Endless Loop In the case of the periodically moving background (waterfall, swing, rocking chair or similar movements, always repeating the same movement) an endless loop can be cemented together from the background film which passes through the gate and in the camera all around the charger or the reels as the case may be. In this case the normal charging of the camera does not need to be altered at all and the endless background film loop runs through the gate in a never-ending way. This loop does not take away any space in the camera, as its only dimension is its thickness and this is negligible. Care should be taken to cement the loop together in such a way that the periodical movement is really maintained and properly bright in register. Otherwise there will be ““jumps’”’ in the period. The splice itself should not show on _ the screen. For stationary backgrounds (such as you use when you have no film strip available and take a shot of a postcard or a still photo) it is enough to have a strip of 5 inches made from the photo in question in the titler and this will serve the background purpose admirably. Some method can always be found to hang this short piece of background film in the gate in such a way that one frame comes exactly into the aperture and the film extends below the claw through the gate so that it lies steady. The perforations are cut away in the area (Continued on page 552) Activities on boats in river or harbour will make a useful sequence for your cine-magazine.