International projectionist (Oct 1931-Sept 1933)

December 1931 INTERNATIONAL PROJECTIONIST 11 cost which seems to be inherent in this type of machine?" It is the purpose of this article to tell what the continuous cinematograph can ■do and offer. Every projectionist is familiar with the erratic behavior of thinspindled, easily warped, high-speed, intermittent mechanisms, when affected by heat, dryness, stickiness or grit. He has witnessed erratic projection with new mechanisms and, of course, he knows how soon precision can be lost because of wear. The fact is, with intermittent projection, steadiness is a variable quantity; and we have all witnessed instances of eye-straining unsteadiness in some of our best theatres. These instances of erratic projection may be traced to the •erratic behavior of the intermittent mechanism, or to the condition of the perforations on the film. With the intermittent principle the registration is absolutely dependent upon the accuracy of every perforation on the film. This is an inherent defect, for it is inseparable from the imperfect and unscientific principle of the registration. It is one of the crudities of the intermittent method, for the film (a non-metallic material), is made one of the most important and sensitive parts of the mechanism. It is employed as a mechanical chain, connecting the frame at the aperture with the teeth of the sprocket. But liow crude its links appear, in contrast with the quality of the material and the finish of the other equally sensitive parts of the precision mechanism. Instead of teing made of the finest steel they are made of thin celluloid, highly subject to wear, to breakage, and to loss of shape. Among the other parts of the precision mechanism this crude chain is an incongruity. But this is not all. Instead of subjecting it to a treatment more in keeping with its crudeness and the material of which it is made, a miracle in the way of performance is demanded of it — precision of a high order at the extraordinary rate of twenty-four severe jerks a second. It is no wonder, therefore, that instances of consistent projection are rare, and perfect projection rarer. And although the crude chain seems to stand the strain, the projection can never be more accurate than its weakest link. So it is worthy of note that the continuous cinematograph offers a real solution to the problem of erratic projection, whether the cause be in the mechanism or in the film. Old and badly worn film can be projected with surprising steadiness and smoothness as the registration does not depend upon the condition of the perforations. Another crudity of the formative or adolescent period of cinematography is flicker. Whether perceptible or imperceptible, flicker is a crudity in motion picture projection for which there is no SPUTTERING AT THE ARC SPUTTERING at the arc may be caused by carbons not being properly set or trimmed, or too short an arc; more frequently, though, it is caused by a damp carbon. Carbons are porous and absorb moisture. They are baked at extremely high temperatures; and when they leave the factory they are thoroughly dry. In shipment, however, they may be exposed to damp weather, or at destination stored in a damp basement. Carbons should be kept in a dry place. A great many projectionists have formed the habit of laying a few carbons on top of a rheostat in order to expel any moisture that might have been absorbed after leaving the factory. Others put a trim in their lamphouses before burning. Either practice is a good one and is to be recommended, as a damp carbon may chip at the crater in addition to causing a sputtering arc. Carbons are not perishable: they will be as good ten years from now as they are today. If they have absorbed water only, they can be dried out in the manner just referred to. However, if a chemical has been spilled on them, they may be rendered worthless, depending upon the nature of the chemical. relating to continuous cinematography lie. And this is possible only because the public does not know it. The "Belladonna Effect" On account of the "Belladonna effect" (the undue dilatation of the pupils when viewing intermittent projection), many instances of injurious practice occur throughout the country. The excessively brilliant light-periods or "peaks" strike in upon an unprotected retina through an aperture or pupil that is much too large for their intensity. This is the natural consequence of the inability of the iris to respond at the high frequencies employed. It becomes more or less fixed or adjusted to an illumination on the retina that is an average of the different intensities of the intermittent light falling upon it. The aperture or pupil thus formed will be suitable for this average brightness, but for no other. Under these artificial conditions the iris fails to adapt the eye to the excessively brilliant lightperiods. The idea that the human eye becomes adapted to intermittent illumination is a mistaken one. Insidious and unnatural conditions attend the artificial adaptation. This can be made more apparent by an exaggerated example — viewing a bright light source through a revolving shutter. By increasing the area of the blade without restricting the opening, a high intensity arc could be viewed directly; but it is obvious that this kind of adaptation would be false and unnatural. But if the excessively bright light-periods in intermittent projection are a crudity, the dark-periods constitute another. The alternations of the two extremes give a screen luminousity curve of which no projectionist will boast. In fact, such a curve will serve to illustrate what a screen luminousity curve should not look like — and why. One of these reasons is that the alternations of brilliant light with darkness form an ideal condi tion for inducing photo-electric effects within the retina. Nerve and retinal fatigue are the only possible results, for they can serve no useful purpose. A defect associated with eye-strain is the loss of definition in horizontal lines, which has become more prevalent since higher rates of projection have been in effect. This is sometimes due to motion or "creep" in the film during the socalled stationary period. A loss of definition in the horizontal lines is so indicative of this condition, that the projectionist will appreciate the fact that the continuous cinematograph actually gives a true stationary period at the highest possible rate of projection. This improves the definition and lessens eyestrain. We hope that we have now pointed out to projectionists the new things made possible through the art of continuous cinematography. It is a new art, and accomplishes new and important effects by novel methods. But there is no doubt that it will become a great art. Its field or scope is broader than that of intermittent cinematography. The restrictions as to the size of frames or the rates of projection are removed, almost entirely. Its flexibility ranges from four frames a second to more than four hundred. This makes possible great advancements in reproducing sound as well as motion. In registration we have shown it to be more accurate, and in the substitution of the successive images, more subtle and scientific. In the future it has great possibilities; but the immediate reality and fact is that this new art brings comfort to the eyes, and adds life, roundness, and beauty to motion pictures. [Editor's Note: Mr. Plank ivill be glad to answer in these columns any question relating to continuous cinematography. Inquiries may be addressed to Mr. Plank in care of this publication. 1