The Moving Picture World/Volume 1/Number 1/The Cinematograph Shutter
The Cinematograph Shutter.
By The Editor.
To use, or not to use, the shutter is a question often uppermost in the minds of operators, and one which has called down more blessings (?) than some would like to own up to. Some operators discard it altogether, regardless of results; others cut it in half and get along after a fashion; others again use two wings; and again, others only one. Out of this multiplicity of methods the question arises, Which is best? We are all striving to abolish the flicker on the screen. Some blame the mechanism of the machine for this; others the film; some the illuminant; and the larger proportion say it is the shutter which is the cause of all the trouble. We are inclined to say it lies with all the above, and that each contention is correct, as far as it goes. But until we get perfection with machinery, that gives absolute correctness in the perforating of the film, a camera which is made to take such film, and the same mechanism, all made from the perfect model, with a shutter adjusted to the requirements of the picture, we shall have to put up with the flicker, or reduce it to a minimum, using the material we have at hand. It is surprising what individual operators use for the shutter, each swearing by his own idea, as though it were of any consequence what material is used so that it is opaque. Brass, zinc, or cardboard all will answer the purpose, and gelatine of various colors for all the semi-transparent ones. Each kind of material visibly affects the light, and the puzzling questions with operators are: What is the proper shutter to use under certain conditions? When should the opaque one be used, or the semi-transparent one, or when to entirely dispense with it? We will endeavor to solve this difficulty by advancing the theory "that it all depends on the light," whether oxyhydrogen or electric, the rule differing in the quality of the same, and the distance from the screen that the machine is being worked.
Let us take, first, the oxyhydrogen (or calcium light). With this the opaque shutter can be replaced by the blue transparent one, if the distance is 30 feet or under, and fairly good results obtained. For over 30 feet—to, say, 65 or 70 feet—it is advisable to use a white transparent gelatine shutter, and for all distance beyond 70 feet good results are obtained without any shutter, although it is advisable to separate the distance from the screen more than 85 feet, as too much light is lost even with the most powerful jets on the market. These figures will also hold good when an oxylith generator is used. The makers of Nulite claim that it is suitable for cinematograph projection, but as we have not tried it we cannot give data, but we fancy that 25 or 30 feet from screen would be the utmost limit for this illuminant.
We now turn to the electric light, where the direct current is used. An opaque shutter is useful up to 50 feet from screen; over 50 feet and up to 100 the blue gelatine is good; from 100 to 150 feet distance the white transparent shutter will be all that is necessary; over 150 feet the shutter can be entirely dispensed with.
When using alternating current, about 20 per cent. of the distances can be deducted, and satisfactory results obtained.
While these figures are not mathematically correct, they will be found to be a very serviceable guide. The operator must, of course, use his own judgment and discrimination in selecting shutter between distances given, and if our readers will test and report the results they obtain it will be useful information for the craft at large, and by comparing data useful and reliable tables may be formulated for future publication.