International projectionist (Jan-Dec 1955)

Tips on Filament Projection Lamps The projectionist craft is finding ever-expanding employment opportunities at non-theatrical showings of motion pictures — industrial, educational, civic, religious and club dates. Many such showings utilize filament-lamp projectors, hence the appended notes on these lamps as supplied by Sylvania Electric Products. PROJECTION lamps are designed to give maximum light output from the smallest, most precise source possible. It is extremely important in the design of projectors or other optical devices to obtain the ultimate in these requirements without sacrificing lamp life or presenting replacement problems. Fundamentally, all filaments used in projection lamps are the same. Since concentration of light is so essential, tightly-wound coils of tungsten wire are used. These coils of wire are then formed into either one or two planes or further wound into coiled forms. Monoplane, Biplane Filaments Every projection system ultimately requires as solid a mass of light as is possible. Lamps with monoplane filaments have spacing between the coils for insulation purposes. In use, one side of the flat plane of the filament faces the condenser, while the other plane faces the reflector. The reflector is designed to refocus the filament image on the same plane as the filament itself, to fill in the spacing between the coils. This results in a near flat plane of light that is collected by the condenser and focused fairly close to the film gate to give the optical system high efficiency. Biplane filaments consist of two planes of coils. One plane fills in the insulation spacing between the second row of coils to give an even greater concentration of light than the monoplane types of filaments. This design permits even closer focusing of the light source to the film gate, for greater efficiencies. All Sylvania biplane filament projection lamps are mechanically formed in special jigs so that each design can be accurately reproduced. High-Quality Glass Envelopes Most projection lamps today have striation-free glass on only one side of the envelope. In fact, government specifications for most projection lamps only require one side of the glass envelope to be free of striations COILED COIL MONOPLANE COIL A O O O O BIPLANE COIL °00OO0°O TYPES OF FILAMENT LAMP COILS and defects. Sylvania lamps, however, are made of carefully selected glass envelopes that are free of scratches, deformed glass and striations on both sides of the filament plane. This insures more uniform light distribution throughout the optical system. Projector Design Requisites All projectors are designed around certain types of filaments and lamp wattages. Naturally, when these are selected the optical system is designed for maximum performance. The use of increased wattage lamps will only appreciably increase the screen lumens until the filament size equals the limiting dimensions of the optical system. After that point the light losses are great and problems are encountered Test Your Electrical I. Q. Here again we present a series of questions bearing on your electrical I.Q. Answer these questions, and then see how your answers compare with those on page 23. (1) What are the regulations for wiring footlight circuits in a theatre as to size of wire, the number of lamps, junction boxes and outlets? (2) What is the minimum size of wire that may be used for branch lighting circuits, and what is the maximum wattage permitted per branch circuit? (3) What is an auto-transformer and where is it used? (4) What is a volt, an ampere, an ohm and a watt? How many watts are there in one horsepower? How many kilowatts equal one horsepower? (5) How would you change the connections to a three-phase motor in order to reverse its rotation? (6) What would happen if a properly fused three-phase motor blew a fuse while running? in dissipating the heat from the lamp, film and optical components. High Efficiency Throughout Life Since projection lamps are the highest efficiency filamentary types of lamps made for continuous burning, it is important that special techniques be used in their construction to guarantee satisfactory performance over their full life. Pressure filling in some of the higher wattage lamps is used to give higher efficiencies, longer life and to reduce bulb blackening. More important are some of the other exclusive features in Sylvania Projection Lamps that serve to maintain the filament in its proper focus position over its full life. Here are some questions and answers relating to the structure and operation of these 16-mm projection lamps : Are They Good for Color Projection? Yes, Sylvania projection lamps are specially designed to produce the best possible rendition of color slides and movies. Each projection lamp filament emits "white" light containing all the colors in the spectrum so that the colors captured in slides and movies will appear on the screen with maximum fidelity. Can I Use Larger Lamps In My Projector? No. Lamps larger than those the projector was originally equipped with or larger than those recommended by the manufacturer may do irreparable harm to the machine and film. The cooling systems of projectors are designed for specific lamp sizes, and the heat generated by lamps too large for the system to handle may damage the optical system and injure the film. Is It Possible To Insert The Lamp Incorrectly? No. Good projection lamp bases are so designed that they will fit the socket only in the correct position. The lamp will slip into proper position immedi•ately, as long as it is not jammed or forced in. Sylvania bases also seat home firmly in the socket, assuring positive contact even during excessive machine vibration. How Long Will They Last? Projection lamps are known as "high efficiency" lamps in the industry. This means simply that they are constructed to utilize their complete wattage so as to provide maximum brightness. Filame»ts of the lamps burn at white-hot 20 INTERNATIONAL PROJECTIONIST • APRIL 1955