Motion Picture Herald (Oct-Dec 1951)

Can’t Buy A GOOD strong Rectifiers are the only rectifiers on the market which are especially designed, manufactured and tested in one plant together with and for use with motion picture projection arc lamps. This is highly important, as efficient operation of each type and rating of arc necessitates a rectifier specifically engineered to its particular requirements. There is a dependable Strong Rectifier for every type projection lamp: 2-Tube • 4-Tube • 6-Tube • Single and Three Phase Models for • Rotating Feed Angular Trim High Intensity • Copper Coated Coaxial High Intensity • 1 K.W. High Intensity • Low Intensity All assure smooth output current, long life, low operating temperature, and flexibility in control. THE STRONG ELECTRIC CORP. CITY PARK AVE. TOLEDO I. OHIO PROJECTION LAMPS SPOTLIGHTS • RECTIFIERS • REFLECTORS GOLDE TICKE DISPENSER FAST . . . ECONOMI Simple and sturdy. Quick dispensing . . . easy reading. Magazine load. AddA-Magazine feature. Rubproof satin chrome top plate. Write for Bulletin No. 467. * At better theotre supply dealers. GOLDE MANUFACTURING CO. ' 1 220-D W. Madison St., Chicago 7 ROBIN-ESCO 'm.G. SET modern . . . DEPENDABLE AND UNFALTERING POWER SOURCE Write for Information and Literature J. E. ROBIN. INC. 267 RHODE ISLAND AVENUE EAST ORANGE. N. J. and here we can easily see the reason why this light is so much out of proportion from normal standard daylight. You can ree that a tremendous amount of the violet and blue portion is actually missing, and that the yellow, orange and red portion is e.xtremely overemphasized. This is the main reason why all low-intensity lighting appears tinted with yellow and sepia color. Since most objects are normally viewed by daylight, a motion picture is most realistic when projected by light from the high-intensity arc. This reaction is quite noticeable with black and white pictures, but it is of extreme importatnce when color features are projected. The necessity for proper color quality of the light used to project our beautiful colored prints cannot be stressed too much. Daylight consists of an essentially even balance of all spectral colors; therefore, to obtain the greatest realism and effect, color pictures are photographed in daylight, or are made under carbon arc lighting of daylight quality. The best effect can only be obtained when these same pictures are projected with light of the same type. The increasing use of color features today makes the proper balance and quality of projection light as important as the proper quantity of light. LIGHT DELIVERY COMPARED Although much has been said and written about the necessity of sufficient picture brightness, yet it is still necessary to drive home this cardinal point, especially in the case of the low-intensity arc. A glance at Figure 4 should be very enlightening. Here are shown two curves representing the comparison between the total projection system light in lumens delivered to the picture screen, and the size of the picture which can be illuminated to a center brightness of the upper and lower values recommended today by the SMPTE Standards. Let us make a few comparisons. A lowintensity arc projection system with shutter running can deliver 1250 lumens to the screen. Looking at Figure 4, we see that in order to obtain a minimum screen brightness of 9-foot-lamberts, a screen 13 feet wide is the largest we can use! If a brightness of 14 foot-lamberts is desired, the screen width must be reduced to 10.5 feet! And this light has a very bad color balance, containing little blue and an excessive amount of red. The 7 mm suprex arc projection system, with new high speed lenses operating at 40 amperes, can deliver 3200 lumens under similar conditions. You can see that a screen over 20 feet wide will have a center brightness of 9 foot-lamberts, and a screen 16 feet wide will have a brightness of 14 foot-lamberts. Here we have made the first and greatest advancement in the art of picture presentation to the public. This one step has done away with a drab yellow, 12-foot picture, and has allowed a beautiful picture from 16 to 20 feet wide, illuminated at the proper intensity with white light. This single change in a theatre has always received recognition from patrons be FIGURE 4 — Screen lumens necessary to give 9 and 14 toot-lambert center screen brightness for screens of different widths. Assuming: 70% screen reflectivity; 70% side to center distribution; 50% shutter transmission; no film in gate. cause it produces evident results. If larger pictures and high brightness are desired, then the lamps can be equipped with 8mm suprex carbons for operation at 60 amperes. Under these conditions, the system can easily deliver up to 5500 lumens to the screen. Now let us examine the operating costs required to produce these various levels of illumination, and let us compare carbon and electrical power costs for low and high-intensity lighting systems. Examine the table in Figure 2, and you will see that column G contains the cost of a carbon trim as used for each hour of operation, including positive, negative, and the leftover stubs. Column H lists the power cost per hour of operation. Here the actual d.c. power used at the arc is figured only, since generators and rectitfiers vary so much in efficiency and d.c. line ratings that no proper comparisons can be made. Column 1 is the summation of G and FI and gives the net operating cost per hour. Column J contains the net operating cost of each carbon trim for a week of 55 hours, which is about average for five days of matinee and evenings, or for two days of continuous operation. The operating cost [Continued on page 36) 30 MOTION PICTURE HERALD, DECEMBER I. 1951