International projectionist (Oct 1931-Sept 1933)

12 INTERNATIONAL PROJECTIONIST September 1932 QUESTIONS AND ANSWERS ON PROJECTION SCREENS Especially Prepared for International Projectionist by R. T. Rasmussen PRESIDENT AND GENERAL MANAGER, BEADED SCREEN CORP. CONSIDERABLE misinformation has been circulated regarding the merits or demerits of various types of motion picture screens of both the silent picture and sound picture types. A majority of projectionists, not possessing the facilities for accurately checking on the various claims advanced for different type screens, have had to depend almost wholly on their own good sense in the selection of screens for their theatres. Most of the misinformation on screens has been broadcast by the major motion picture theatre circuits in the form of solemn pronouncements by well-meaning but misinformed projection supervisors, in circuit house organs, in bulletins and in "orders" issued by division managers. The appended questions and answers, the first of a series to appear in these columns, are not intended to be controversial or to constitute a rebuttal of screen facts from other sources, but represent the results of careful tests conducted by competent workers using every modern testing facility. — Editor. 1. What is a Sound Screen? A sound screen is a motion picture projection surface porous or perforated to allow free passage of sound from the speakers placed at the back of the screen. 2. What is a Perforated Screen? A Perforated screen is a fabric, coated with white pigment. Holes are punched through the material at intervals averaging 5/16 inch. Each row of holes is staggered over the center of the adjoining row. The back is usually tinted in various colors. This color is for identification purposes only, and does not affect the projection quality. Perforated screen fabrics are, essentially, what are known as Pantosote or Fabricoid. The base fabric is cotton cloth coated with a celluloise compound (celluloid). All perforated screens are essentially alike in construction and reflection characteristics. The largest bulk of this fabric is made by one manufacturer of Fabricoid materials. The projection qualities and the useful life of a perforated sound screen, is, for all practical purposes, identical. The perforated space area averages from 5 per cent to 8 per cent of the whole area. 3. What is a Porous Screen? A porous screen differs from the perforated type in that the sound passes through the screen via interstices in the woven cloth. In the Vocalite and Chromolite type of porous screens, there are also tiny eyelets woven in at i/4 inch in^ tervals in staggered rows. The area of sound openings in a porous screen ranges from 25 per cent to 30 per cent of the entire area. Porous screens offer no resistance to the transmission of sound, even at the high frequency ranges. 4. What are the trade names of perfor ated screens now on the .market? DaTone X Walker DaTone Z RaTone Datone B Minusa DaTone F.P. Gardner Superlite Orthochrome HORN PLACEMENT AND terest take the same form; people stay POROUS SCREENS away. As for the perforated screen — it may be clean, it may be white, yet if it is compared, from any normal viewing disstance, with an unperforated piece of the same material, the latter will appear cleaner and whiter than the perforated sample. The perforated screen produces a sort of "half-tone" effect to even a sharply defined picture, and when this effect is compounded with a soft-focus effect that may look very artistic on a solid screen, the result is something that must be decidedly conducive to eyestrain. As regards horn placement: some time ago, when the matter of attachment sound systems was being discussed in committee, one of the engineers exclaimed, "The trouble is that we are attempting to fit a precision instrument to a machine that is not a precision device." He spoke very truly. The trouble is that a precision industry is trying to fit itself to an industry— the exhibition of motion pictures — that is not a precision industry, and that apparently strongly resents any and all attempts to make it so. Almost any service engineer will admit that practically all the cooperation he receives from the exhibition phase of the industry comes from the projectionists. The majority of exhibitors are either apathetic or antagonistic. Many want service abolished altogether, want to sever all connections with the precision industry. Therefore, any recommendations that the Society may make as regards the placement of horns or speakers will receive but scant cooperation from the exhibition phase of the industry unless it effects a considerable saving. Quality will not be considered. 5. What are the trade names of porous screens? Super Vocalite Chromolite 6. What is the difference between vari ous perforated screens? There is no essential difference between perforated screens. The greater bulk of the base material is manufactured by one company to one standard formula. The light and sound characteristics of perforated screens are for all practical purposes identical. Perforated screens range from 71 per cent to 79 per cent in brightness. It frequently happens that one panel of a screen will vary from 5 per cent to 10 per cent in brightness from one end to the other. 7. What are the trade names of Beaded Screens? There are two beaded screens on the market : Super Vocalite Brightness percent 187 DaLite Beaded " " 115 8. JFhat is a Metallic Screen? A metallic screen is a reflective type of screen using a cotton fabric base, coated with aluminum, or combinations of aluminum, mica and gold bronze. 9. What is a Silver Screen? A Silver Screen is the same as a metallic screen except that the coating is aluminum only. 10. What is a Gold Fibre Screen? The so-called gold fibre screen has an aluminum coating in which has been mixed various proportions of gold bronze powders giving the finished screen and the projected picture a yellowish golden tinge. 11. What is a diffusive Screen? A diffusive screen is a white matt surface, which reflects light equally in all directions. Consequently, a person sitting at a wide angle with respect to the screen receives as much light as the person sitting directly in front. 12. Where should a Diffusive Screen be used? In houses where the projection angle is greater than 20 degrees. It should as a rule always be used with hi-lo or high intensity lamps. A diffusive screen is best adapted to wide houses where a large proportion of the seats are at angles of 30 degrees or more with a line normal to the center of the screen. It must be remembered, however, that eveness of reflected light is being secured at the cost of the strength or intensity of reflected light over the largest area of the house. Advantages of a diffusive screen are: (A) It reflects a large percentage of the projected light. It is very efficient. (B) It is good for color projection. (C) It reflects the projected light through wide angles, giving satisfactory projection for wide theatres. (D) It is efficient in theatres with steep projection angles. [There exists widely divergent opinion as to the relative merits of projection screens. Discussion of the questions and answers which appear herein, or additions thereto, are solicited. — Editor.] (To Be Continued)