Exhibitor's Trade Review (Sep-Nov 1921)

1408 EXHIBITORS TRADE REVIEW Volume 10. Number 20. PROJECTION More Light on Continuous Projection By C. Francis Jenkins Such an assumption seems paradoxical, but it may be accomplished by employing a long strip of glass prism section with e base up at one end and base down at the other end and a gradually changing contour from end to end between these two extremes. (See Fig. 2.) If this strip of glass is passed across the path of the s t or 1/f Fig. 2 film, in the light cone and in synchronism with the travel of the film, the constantly running film will appear stationary on the screen when used as a projector. But to make the continuous motion machine of these elements the strip of prismatic glass must be made into a ring (in the plane of its width) with the two ends abutting. When this is done, the contacting ends (R, Fig. 3) represent crossed prisms, one with the base (S) outward and the other with the base (S) toward the axis of rotation of this ring. As a matter of convenience in fabrication, this ring prism is actually ground in the face of a disc of glass, as you will observe, for this then makes its own support on the rotating shaft, upon which it is mounted. This ring is so geared to the film-feeding sprocket that it makes one revolution with the passage of each single frame across the aperture, and, of course, in exact synchronism therewith. The median line of the prismatic ring, the objective, the picture aperture, and the light source are all located in the axis of the cone of light, the prism being located at the point where the hinging or bending of the light cone is to be effected. As explained above, the ring makes one complete revolution for the passing of each picture frame, and in synchronism therewith, each frame instantaneously dissolving into the next as the joint in the prism ring crosses the light cone, so that the picture on the screen is stationary, continuous in action and without interruption by shutter blades. Observe that the machine employs standard film, stock objectives and condensers and the usual light source, all readily changeable as to size, focus, etc. However, as noted, it does not have the usual fifty-fifty rotating shutter necessary on the intermittent machine, and so the incandescent lamp may be expected to have still further usefulness for there is 100 per cent increase in screen lighting ef-' ficiencies. It is not my intention to suggest that the problem is solved to an extent precluding further improvement, but I do think any work along this line is worth while. THEATRE PROBLEMS Owners and managers of Motion Picture Theatres are invited to send in their problems to this department. They will be answered without charge and as fully as possible. Reading Color Scale Theatre Problem Dept.: Will you inform us how we may read the color scale without going to any great expense to do so? We have read your recent articles of screens and never knew before what a deep subject the screen presented. Charles and Walter Joyce, 1201 Market St., St. Louis. We have found in a booklet issued by the Minusa Cine Screen Co. of St. Louis a very simple method of reading the color scale together with a diagram of the same. Throw your light frame down on your screen and freeze your carbons; you can read the color scale as easily as any expert can. Here is a chart which gives an approximate idea of how light color changes. Colors enumerated predominate only at the distance shown. Thus you can easily see how the various size of pictures, various lengths of throw and the known variations in color characteristics of A.C. and D.C. light change the color of the projection light at the point of contact. Screens (Continued from page 1406) image. Brilliancy at the cost of a loss of perspective and detail is entirely undesirable. Increasing or decreasing the amperage proportionately increases and decreases this haze or reflection. This result is also common on gold screen surfaces under certain conditions of projection, unless a colored background underneath the surface finish is used. Our method of proving these assertions is to photograph the light rays from the projection machine from a side angle as they strike the screen surface. When the projected light from the arc strikes a surface of exactly the same color as it is, there is absolutely no refraction or fuzz registered on the plate, or photograph. This is not a complicated scientific theory; anyone with a slight knowledge of the color characteristics of projected light knows the spectrum of such light is composed of the three primary colors, red, blue and yellow. Of course, the various combinations of these three colors make green, orange, violet and a score of other tints and shades. Just use your own knowledge of projected light and remember our reference to the sunlight striking the snow. Here's the proof: Throw your light frame down on your screen and freeze your carbons; you can read the color scale just as easily as we can. At 5 feet the light color is violet, 25 feet purple, 50 feet red, 75 feet orange, 100 feet dark yellow, 125 feet light yellow, 150 feet very light yellow, 175 feet white yellow. Thus you can easily see how the various sizes of pictures, various lengths of throw and the known variation in color characteristics of A. C. and D. C. light change the color of the projected light at the point of contact. In addition to this, wide house conditions require expert color shading. More than sixty distinctly different formulas, ranging in surface color from a dark reddish gold to a very light shade of yellow, are used to meet the various conditions described. The surface color of the screen we build must match perfectly the color of the light at point of contact. The texture of surface finish must vary from a fine grain to a roughness that will harmonize and utilize the side angle reflection which practically eliminates the fadeaway and distortion when viewing the picture from an extreme angle. Ten Thousand Dollars Reward will be paid to any person who can prove that B. F. Porter did not sell and install Simplex Machines in the Capitol Theatre at 51st Street and Broadway, New York City. B. F. PORTER, 729 7th Ave., New York