American cinematographer (Sept 1935)

396 American Cinematographer • September 1935 Negative-Positive Home Laboratory M ore and more, the serious worker in 16mm film is turning to the negative - positive process in preference to the reversal process because of the many advantages it offers; such as, an unlimited number of copies of equal quality, wide latitude in exposure for special effects, the possibility of introducing many trick effects in the printer, and a negative to preserve. The one objection to this process in the past, graininess, has been largely eliminated by the film manufacturers who now offer 16mm negative stock which will produce pictures of excellent quality if handled correctly. It is the purpose of this article to give the beginner sufficient information so that he can do his own laboratory work, as many serious workers prefer, or to understand the process well enough to use it successfully when the work is done by a commercial laboratory. First, let us consider the equipment needed to develop and print 16mm film. Some type of drum or rack with tanks for developing the film, a drying drum, a printer and a dark room lamp complete the necessary equipment outside of chemicals—and a scale to weigh them if the worker wants to compound his own. Many of these items can be made by the worker, so the cash outlay need not be great unless it is desired to process a large amount of film. The first item, the developing drum or rack, together with their tanks is one of the most important items. There are several special reel and tank outfits on the market which can be bought reasonably and which will do the work nicely altho they do not permit ready inspection of the film during development. They also require careful handling of the film in transferring to the drying drum. The writer believes the beginner will find the drum system the easiest to handle safely and one that can be easily made at home. The accompanying photograph shows such a drum together with its tank. The drum can be made of wood of such size as the worker may desire (the one shown holds 50 feet of film) with wooden dowel pins set in three of the bars to space the turns of film. The whole is well painted with a black waterproof enamel. The tank in which the drum revolves is best made of stainless steel with welded joints, altho other metals (such as brass or galvanized iron) with soldered joints can be used if the whole tank is given several coats of good waterproof enomel. The enamel should be inspected frequently and touched up when it becomes chipped. Three tanks will be required, one of which should have a tube for attaching a hose from the water faucet for washing the film. The drying drum can be a skeleton affair supported so it can be revolved in winding the wet film onto it from the developing drum. It can be only a four bar "drum” if simplicity of construction is desired. The printer is the most elaborate piece of equipment needed but even it can be built from a small projector or camera similar to the one described in the June 1935 issue of the American Cinematographer. Of course, the details will have to be altered to fit the type of projector or camera being used; the main things to secure being good contact between the two films, uniform speed of the motor drive and a means of changing the intensity Work by Charles E. Keevil of the printing light. If possible, it is desirable to be able to watch the picture being printed at the aperture so as to change the printing light as the scene changes. If the camera or projector being used will not permit this, the negative film can be notched on one edge at the scene changes and a lever put on the printer to ride on the edge of the negative film—when a notch comes through, the lever will drop slightly and can be arranged to give a signal for the light change. Commercial printers automat- ically make the light change when the notch passes the lever, but that will complicate things too much for the home constructor unless he is well equipped with tools. If the printer is run at a speed of about 8 frames per second (half camera speed) the operator can make the light changes by watching the picture in the aperture or from the signal. If one is well supplied with cash, there are several good 16mm printers on the market. A dark-room lamp with both red and green safelights, chemicals, scale (if used), bottles for the storing of solu- tions, and a small viscose sponge complete the equipment. Half-gallon fruit jars of the glass top variety are excel- lent for storing developer and hypo as the rubber ring seals them air-tight. The viscose sponge should be cut in half, so as to have two thin pieces for removing excess water from the film when it is wound onto the drying drum. Making the Negative All the large film manufacturers make 16mm negative altho they don't seem to advertise the fact and many do not know about them. Eastman, Agfa and Gaevert make a regular speed panchromatic negative which is about Vi stop faster than regular reversal panchromatic film while Du Pont makes both a regular and a "Special" or super- sensitive panchromatic negative, the supersensitive being about 1 stop faster than the regular or 1 to 1 Vi stop faster than regular panchromatic reversal. A good exposure meter is a big help—if a Weston meter is used, o film speed factor of 16 for the regular negative and 24 for the Speeial is about right for daylight work. All these films come on daylight-loading spools and are loaded in the camera in the same manner as the reversal film— a difference in the film will be noted as the non-halation coating on the negative is much lighter in color, not the heavy black as found on reversal film. Loading of the camera should be done carefully, especially with the super- sensitive film, to avoid edge fog. In order to gain familiarity with the equipment, the