International projectionist (Jan-Dec 1958)

next slide to be shown without attention by the operator. By the use of a remote cord, the user may bring each slide up for viewing at irregular time intervals by using the button provided.* This arrangement complements the use of a pointer on the screen, and permits the person showing the slides to remain near the picture. Such positioning allows the explanatory comments to issue from the vicinity of the picture, and almost everyone is conditioned to such an arrangement due to the placement of the sound reproducing units. The advantages of the automatic tray-loaded slide projector justify its additional expense. By removing the principal causes of the film damage, we render a real service to the A-V field. We who are active in this area simply cannot tolerate streaks, scratches, finger-marks, or dirt on the film. By resorting to the tray-type projector, we may eliminate the handling of individual slides. This means that pictures are available properly oriented and in correct sequence, which is the prime advantage of the filmstrip. The use of the automatic tray-loaded projector is a great A-V aid. Use It ! *See announcement re: Kodak Cavalcade projector extension cord elsewhere herein. New Sylvania Tru-Flecror 8-mm Project-ion Lamp In standard projection systems (Fig. 1) a reflector behind the lamp and a condenser in front of the lamp are used to collect a small portion of light to direct it onto the film. The light that passes through the film is then collected by the objective lens and directed onto a viewing screen. The efficiency of such a system is usually determined by the amount of light (or solid angle of light) collected by the condensers providing they match the rest of the optical system!. Unfortunately, mechanical limitations and high costs ■I FILM GATE ^ffloff CONDENSER OBJECTIVE LENS LENS IP Service Bureau Film Cleaning Methods A recent survey by IP disclosed that much valuable film is being damaged, sometimes irretrievably, by the use of improper cleaning fluids. Once damaged, a given film subject is removed from circulation for an indeterminate period of time, thus frustrating the aims of the sponsor and the teacher. IP is now prepared to give authoritative data as to the best method for cleaning any film base, irrespective of character. These data are based upon an exhaustive survey conducted (cost-efficiency basis) by one of America's foremost research laboratories. FILM GATE LAMP FIG. 1. Conventional projection optical system. OBJECTIVE LENS LAMP FIG. 2. Sylvania Tru-Flector Optical system. prohibit the design of highly efficient systems. The specially designed Sylvania Tru-Flector lamp eliminates the need for external reflector and condensing lenses formerly used in projection equipment. This new concept enables a 150-watt lamp to perform equally as well as former 500watt lamps — effectively increasing lamp efficiency over 300%. The Tru-Flector lamp (Fig. 2) not only simplifies the optical system of a projector but greatly increases its efficiency. The special silvered reflector acting as a condenser collects almost a full hemisphere of light emitted by the special coiled coil-filament and directs it onto the film. At a rating of 150 watts this lamp will perform equally as well in 8-mm projectors as one three times its power with conventional objective optics. Its short focal length and special reflector make it ideally suited for use with a 22-mm, /:1.5 objective lens. Use of an auxiliary transformer with this lamp enables the manufacturer of 8-mm projectors to ex LAMP VOtTAOe Comparative characteristics of the 8-mm TruFlector projection lamp. ert greater control than ever before over the lighting characteristics of his equipment. He may select whatever combination of lamp brightness, life, and operating voltage he desires, and order transformer settings to conform. For example, the transformer could convert standard household voltage of 120 to a 21-volt lamp operating voltage. With a 1-inch /:1.6 objective lens, this would produce projector light output of 150 openshutter screen with an average rated life of 15 hours. Graflex 35-mm Slide Unit A new remote-controlled 35-mm slide projector, utilizing a unique slide pre-conditioner which prevents slide popping, has been announced by Graflex, Inc., o f Rochester. It will be known as the Constellation Mark II. The Mark II has a specially designed, highly efficient lamp, optical system and cooling system. It has a smaller, excellently cooled new Tru-Focus lamp which is pressurized for longer life and increased brilliance. A 4-element optical system makes maximum use of the lamp's brilliance through the transparency and onto the screen. Slides pop out of focus as a result of the very rapid temperature change that takes place when a cold slide is exposed to sudden heat from the projector lamp. By providing warm air, carefully tem Groflex 35-mm slide projector 16 INTERNATIONAL PROJECTIONIST • OCTOBER 1958