Motography (Apr-Dec 1911)

178 MOTOGRAPHY Vol. VI, No. 4. be easily produced ; but then, even illumination of the field becomes more difficult, and brilliance is lost. Large apertures and short tubes will allow the greatest amount of light to get to the screen ; the illumination will then be brilliant and even, at the expense of critical definition. After all, the projecting-lens is again a compromise, like the condenser, and the perfect projecting-lens is yet to come. Improvements are still being made in projection-lenses, but the poor, haphazard condenser remains in the same condition as formerly. Condensers break more or less often, owing to the heat to which they are subjected, and as at present made, are inexpensive to renew ; which facts probably account for their being considered good enough for their purpose. The time will, no doubt, arrive when the condenser will receive more attention, and when in consequence breakages will be fewer, illumination will be better, the film and machine will not become so heated, and the electricity bill be reduced. Now, let us return for a short time to theory, and suppose all items in a projection system to be perfect, the conditions of perfection being the following: 1. Illumination to consist of a point of light of sufficient brightness. 2. Condenser to be free from aberrations, both chromatic and spherical. 3. Film to be quite clear in those parts intended to show white on the screen. (By this I do not mean that there should be large clear spaces on the film, but that only those parts which are the brightest should be clear. A large expanse of sky should seldom or never be quite clear; clouds or small patches in the foreground generally appear in nature brighter to the eye than does a clear blue sky). 4. Projecting-lens of sufficient aperture to allow all the rays which come from the condenser through the gate opening, to pass direct to the screen. 5. As an extra refinement, the condenser to be out into regular shape, proportionate to the shape of the film mask, or to have a suitable screen of asbestos card placed between it and the light. Then only the rays required to illuminate the film mask would get through the condenser and much heat would be saved. Such being our theoretically perfect conditions, will proceed to adjust our supposed apparatus. First, the distance from the screen must be settled, and taking this distance as one of the points of the conjugate foci of the projecting-lens, the film must be made to occupy the other. The condenser must then be placed at such a distance from the film that straight lines drawn from its sides and corners to the corresponding sides and corners of the film mask will, after passing through the center of the middle of the tube of the projecting lens, strike the opposite sides and corners of the picture on the screen. The illuminating point must now be placed at such a distance from the condenser that its conjugate focus point on the other side of the condenser falls just where all the straight lines cross inside the projecting-lens tube. The foregoing conditions are the theoretically perfect ones to be aimed at. Owing to the imperfect conditions of our optical appliances we cannot get very near the ideals here set out, and in some cases must purposely depart from them to get good results. First, our illuminant is not a point, and the rays it sends out are consequently not caused to pass through another point, but generally through another space considerably larger than that from which they emanated. Second. The condenser does not bring rays from a single point to another single point, but to a succession of points forming a line more or less long, according to the amount of spherical aberration present. We thus have the rays from several points forming a number of lines in the projecting-lens, and making a large space in which the rays cross, or try to cross, and reach the screen. Some of these rays never enter the projecting-lens; they tend to cross either too soon or too late, while others which enter the tube do not get out, because they cross too soon. Third. A great many rays which pass the condenser get no farther than the film mask. The condenser forming a circular cone of rays, all cannot pass through a rectangular aperture which is smaller than the diameter of that part of the cone, which cone necessarily is made inordinately large to keep the outside colored rays clear of the corners. But all these unusable rays carry heat with them, especially the colored outside rays, which help to heat up the gate and the machine; and, as before pointed out, many rays pass through the film and are unable to get through the projecting-lens. These also carry their share of heat, to which the unlucky film is subjected and from which neither it nor the screen derives benefit. I am afraid I have made out rather a bad case for our present projection outfit. I hope its improvement may claim the attention of some of our inventors. Chicago Censors Have New Idea Chicago police censors have recently been wondering why the film can't come to them to be inspected instead of the censors going to the films. A number of aldermen are behind the movement in addition to Censor O'Connor, who approves most heartily. The change is desired so that Censor O'Connor may actually see the pictures he is asked to pass upon. At present he never leaves the city hall, but depends upon the advice of subordinates, of whom there are seven. It is their duty to visit all places where films are shown and inspect them. Under the new arrangement all films will be inspected in the city hall. Alderman Bauler believes the inspection force can be reduced to four members. A film company has agreed to furnish a moving picture machine to be used in the city hall. "Later," said the alderman, "I will introduce an ordinance in the city council establishing a regular board of censors and providing for a charge of $1 for each picture examined. This will defray the expenses and tend to keep out objectionable pictures because of the fee." Motion-Picture Snows m Scotland Consul E. Haldeman Dennison states that although there are 16 moving-picture shows in Dundee, the majority are small, their admission charge being 2 to 4 cents. The largest amusement company operates 16 theaters in Scotland ; this concern is replacing all other kinds of machines with a Chicago motion-picture mechanism. Just at present American "Wild West" scenes are very popular in Scotland and a great many American-made films are used.