International projectionist (Jan 1963-June 1965)

Booth Left Projector Assembly with Sound and Control wiring Channel Box Method shown. W5-17 optical amplifier with monAural phonograph input, pre-amplifier PA input, mixer or FM radio and the fourth channel stereo magnetic pre-amplifier switcher. Normal function of the Amplifier is optical sound from number 2 stage center speaker. Stereo-phono record player reproduction ( 2 channel ) is used for inter mission or incidental music recordings. A novel and enhanced reproduction effect is secured from stereo recorded records through use of the number 2 stage channel speaker for the number 1 channel stereo and the Hi Fi flush ceiling "surround" speakers for the number 2 stereo-phono channel. The public is very congnizant of the improvement in sound reproduction quality, often question ing whether recordings heard are from tape or film. The Cinema Theatre auditorium has some "live" acoustic resonant tendencies at voice fundamental frequencies due to the absence of drape or wall fabric materials on side and rear walls or ceiling. Acoustic plaster is used over the rear curved auditorium cement wall. The ceiling consists of eleven tilted panels in three large sections. These panels consist of steel angle iron frames and metal lath, covered with acoustic plaster. They are spaced from and suspended by steel wire and anchor bolts from the pre-cast concrete ceiling beams and cement beam stems. This spacing and "tilt" installation provides a variable acoustic pocket but with negligible surface absorption. The side walls to ceiling consist of perforated and corrugated aluminum over fiberglass insulation, decorative as well as fireproof. Resonant damping so acoustically desirable to securing intimate screen presence from stage speaker reproduction is minor, but the decorative effect and new commercial materials design is modern and unique. Indirect auditorium lighting is provided around ceiling panels and is best controlled using conventional Mazda multi-colored tungsten lighting strips and motorized dimmer. iP XENON Projection Lamps Continued from Page 10 mirror, the light will become bluish — an excessively high color temperature. In either case, the light will become annoyingly dim. Xenon Arc Always Daylighr-Whire The xenon arc is free from both these causes of color change. It emits light having a constant color temperature of about 7,000° regardless of current changes, which affect only the brightness of the emitted light. There are no variations in color over the emitting area ( the xenon arc between the two tungsten electrodes ) , and there is no burn-away of electrodes to introduce disturbances in the optical focus. Though smooth and continuous, the spectrum of the high-pressure xenon discharge reveals a moderate emission peak in the blue; but the spectrum has no dark gaps; and the blue peak introduces no perceptible visual effects or distortion of the colors in color prints. The invisible portions of the xenon-lamp spectrum produce unimportant physical effects. Xenon radiation is proportionately richer in ultraviolet radiation than is the HI carbon arc, and quartz transmits ultraviolet rather freely. Ultraviolet rays act upon the oxygen of the air to produce ozone, a gas which is perceptible to the projectionist by its chlorine-like, but not unpleasant, odor. Ozone does no harm in the small quantities produced by projection light sources. just beyond the red end of the visible spectrum 16 of xenon we find a rather large energy peak. This is in the infrared region. Infrared rays contribute nothing to the luminance of a light source, but increase the heating effect of its radiation. The xenon infrared peak is nevertheless neither intense enough nor broad enough to require use of heat filters where these would not be required by other considerations. Lumen for lumen, xenon radiation is a trifle more heat-producing than HI carbon-arc radiation, rather cooler than LI arc radiation, and considerably cooler than tungsten-filament radiation. Its color temperature of 7,000° K makes xenon light an extremely close match for diffused daylight or Standard Source C. The match is probably exact after the xenon light has passed through film, lenses, and port glass, and undergone reflection from the screen surface as well as from the silvered lamphouse mirrors, all of them elements which tend to yellow the light and thereby lower the color temperature. It is interesting to note that diffused daylight (approximately 6,500° K) has been chosen as the standard white for both black-and-white and color TV picture tubes. The physical structure and operation of the xenon short-arc bulb will be described next month — mighty important considerations for the thousands of projectionists who may soon be called upon to operate this clean, convenient, and very pleasing light source. (To Be Concluded) International Projectionist June 1963