The Exhibitor (Aug-Nov 1948)

St. Louis Sights {Continued from page 7) the negative arc stream within the crater of the positive carbon. Thus a substan¬ tial portion of the brilliantly luminescent vapors emanating from the negative car¬ bon produces a snow white light of very high candle power, much brighter than is possible to obtain otherwise.” Long Tail Flame To repeat, the most distinctive feature of the burning action of the electronic arc is a long narrow tail flame rising at a slight right angle to the arc. The tail flame of the suprex arc burns with some¬ what of a mushroom effect, at a short forty-five degree angle to the arc. A point about the new arc that you will want to be sure to examine is the elec¬ tronically-impelled carbon feeding mech¬ anism, which is constant. This patented device was developed before the engineers stumbled on the new burning technique, now also patented. It is through the feed¬ ing mechanism that carbon consumption is said to be cut down — by as much as from twenty to twenty-five per cent. Elec¬ trical power savings are proportional. Electronic Carbon Feed Summing up, the makers say that “the true high-intensity effect” of their arc “is accomplished by a combination of three factors: proper air stream admitted at the proper point with relation to the arc, electronic directional arc control, and proper and constant carbon feeding mechanism.” CORNING FILTER While on the subject of arc lamps, which, incidentally, exhibit the only radi¬ cally new units and procedures in the entire projection field, we insist that one of the most spectacular developments has been the water-jacket or air-blower cool¬ ing of huge arc lamps at the largest di'ive-in theatres. These lamps make use of the terrific advantages of one hundred and fifty to two hundred ampere, eightyvolt projec¬ tion. The extreme requirement, two hun¬ dred amperes, has been used sparingly, but it has been used. With these giant arcs, air-cooling is the general practice. The new technique involves the pass¬ age of light through an infra-red filter, PT-18 which stops the infra-red as well as heat rays. The rays are hot enough to melt any known transparent substance — with the top-spot exception of a glass put out by the Corning Glass Company. The glass is composed nearly entirely of pure quartz. The tough mineral comprises the filter itself, which is thus enabled to withstand both the extreme heat rays and the drastic strains of alternate heating and cooling. The “air-cooling” term means merely that a stream of air is played upon the filter by a fan. The biggest lamps in which the filter is not a requirement are the standard seventy-ampere, forty-volt types. This is the absolute maximum intensity of arc light that it is possible to project safely through motion picture film without em¬ ploying the infra-red filter and attendant air or water-cooling devices. We are not sure whether one of these extraordinary Corning glass filters will turn up in a machine at the show or not. But if one does, you should certainly view it. STRONG SPOTLAMP In an allied field, followers of arc-light projection will want to drop in on the Strong Electric Corporation exhibit, where will be unveiled an improved line of arc spotlamps, according to what we are told. A variety of sizes of high-intensity, reflector-type spots for a variety of pur¬ poses — from circuses to theatres — will simultaneously be put on the market. The same light source used for motion picture projection plus “an ingenious two-element, variable-focus projection lens system,” the company says, “results in uniform lighting efficiency and clean sharp edges from head spot through to full flood.” “Light weight construction and delicate balance permit one-hand control and easy following of the fastest action,” the makers add. “The spotlamp can be swung through a full three hundred and sixty degree radius and compressed to angles of forty-five degrees or more.” The spots are reported to be set up with a color boomerang, fading iris, ultra-violet filters, and simplified automatic carbon feeding mechanism. The masking control has both vertical and horizontal adjust¬ ment blades, capable of angles up to fortyfive degrees. When the lamps are put in, projection room temperatures are lowered, because only a small rectifier is required for arc power. NEW BALLANTYNE LINE If for nothing else, the name of the TESMA show should be kept green by the Ballantyne Company, which has a com¬ plete new line of “Royal Soundmaster” and “Royal Lightmaster” products — im¬ proved soundhead, improved arc lamp, improved rectifiers, new two-way horn system, and for the first time, a projector. A recognized leader in sound, the com¬ pany has added a good-looking soundhead of clean lines, called the Model Eight, to its line. Production of the more moderately-priced Model Six will be continued. Most distinctive feature of the new soundhead is a gyro-filter designed by a Ballantyne engineer — F. C. Largen, Sr., of the Creighton, Nebraska, plant. Incorpor PHYSICAL THEATRE DEPARTMENT of THE EXHIBITOR Improved Soundhead ating what is said to be “perfect gyroscopic action,” the filter is responsible for “abso¬ lutely smooth film travel over the rotary scanning drum.” It contains all steel units, ball-bearing mounted and permanently sealed. In operation, Ballantyne boasts, it is “positively fool-proof.” Two other features are a motor attached to the main frame casting of the soundhead and a handwheel affixed to the front of the motor housing. This last is for convenience in threading soundhead and projector. Lightmaster Arc Before reporting on Ballantyne’s im¬ proved high-intensity arc lamp, model 4570, present problems of light projection should be recalled. Hollywood is concen¬ trating more and more on the development of sharper light and shadow contrasts in motion picture film. This creates film of greater density, and, as a direct result, a heavier drain on the light source. Color film demands also are high. “The lamp you buy today may not be sufficient for tomorrow,” the company re¬ minds theatremen. Its product has “reserve amperage for outstanding contingencies” above and beyond best normal light re¬ quirements for any house. The Ballantyne lamp has a fourteeninch Bausch & Lomb reflector at a thirty two-inch working distance. The reflector is designed to perform with f/2.0 lens. The projectionist may select the amper¬ age needed — from forty -five to seventy amperes — by setting the rheostat for the called-for positive carbon feed, and by simple adjustment of the negative carbon micrometer drive, if need be. “Obsolete, troublesome electro -magnets are replaced by a steel loop, mounted on the carbon guide,” the makers explain. The loop is magnetized only when the arc is New Horn September 22, 1948