International projectionist (Jan 1961-Dec 1962)

lengths at one end of the visible spectrum, and of red wavelengths. Stated another way, a natural source of pure white light (the sun or the HI carbon arc) emits more strongly than the imaginary equal-energy source in the green and yellow spectral regions to which the human eye is most sensitive. Xenon Lamp a "Hot" Source Now, every known light source suitable for motion-picture projection emits invisible radiations which are just as heat-producing as the visible ones we know as "light."** These are the ultraviolet rays beyond the violet in the shortwave end of the visible spectrum, and the infrared rays beyond the red in the longwave end. Fig. 1 illustrates in the form of a spectrophotometric graph the ultraviolet, the visible, and the infrared bands of radiation emitted by two widely used projection illuminants, the HI carbon arc and the xenon gas lamp. Figure 1 reveals that the infrared radiations of these two sources produce much more heat than the comparatively small amount of ultraviolet radiations present. The ultraviolet is chemically active and exerts a bleaching action upon color-film dyes; but in the case of the xenon lamp, the excessive ultraviolet radiation is removed by the use of ultraviolet-absorbing condenser lenses or by means of a dichroic "cold" mirror. The hot infrared radiation is harmful to both film and mechanism, and, of course, is useless to projection because it contributes nothing whatever to the brightness of the picture. In regard to this, it is of interest to note that the zenon lamp, because of the broad peaks in its infrared spectrum, is many times more heat producing, lumen for lumen, than the HI carbon arc. In fact, the xenon lamp is even hotter, lumen for lumen, than the old LI carbon arc, but not quite so hot as tungsten ("mazda") illumination. Emission of Visible Radiations Although the character of the ultraviolet and infrared spectra of projection light sources have a bearing upon the overall efficiency of the illuminant and indicate whether heat filters or dichroic mirrors should be used, the brightness and color of the illumination depend solely upon the spectrum between the shortwave extreme of 400 nanometers (violet) and the longwave extreme of 750 nm (red). As a matter of fact, the significant portion of the visible region **The term "visible light" is tautological, inasmuch as the word "light," alone, implies visibility. It is therefore undesirable to speak of the invisible electromagnetic radiations (Xrays, ultraviolet, infrared, and radio waves, etc.) as "black light" or "invisible light." We have frequently pained the purists by committing this philological peccadillo. Kalart/Victor Projectors Help Sell Porter-Cable Suburban Riders PorterCable Machine Companychose Kalart/Victor as the best possible 16mm sound projector for use by its distributors in presenting an important new sales film on riding mowers and tractors. Here's why: 1. Simple threading a key requirement. Porter-Cable needed a projector that can be threaded and operated by people with no previous experience. Kalart/Victor meets the need perfectly. It is threaded in 3 simple steps, with a color-coded path to show sequence and location. 2. Film safety important to Porter-Cable. No projector guards against film damage more effectively than a Kalart/Victor. Safety Film Trips— an exclusive feature— stop the projector in emergencies, before film is damaged. world's most experienced manufacturer of 16mm sound projectors VICTOR ANIMATOGRAPH CORP. Division of KALART Plainville, Connecticut 3. Can it be set up anywhere? PorterCable likes the top-mounted reel feature of Kalart/Victor projectors. With both reels out of the way on top of the projector, any level surface may be used for setup. Projectors were made suitable for use even in small rooms since they were purchased with llA" lenses instead of the standard 2" lenses. What features are you looking for in a 1 6mm sound projector? Great -picture quality? Magnificent sound reproduction? Outstanding durability? Adaptability for magnetic recording and playback? Kalart/Victor has them all — and more to boot. Call your Victor Dealer for a demonstration. free booklet how Industry Profits from Sound Films. Send today for your copy of this practical booklet. Dept. 203 International Projectionist January 1961