Boxoffice (Jul-Sep 1947)

Dear Subscriber: Please put a marker here and pass this issue on to Projection Room CINE' nine PRACTICAL DISCUSSIONS ON MODERN PROJECTION AND SOUND PRACTICES constant manual adjustment of the controls. But even a larger capacity lamp, operating at the top limit of 65-68 amps with a 14-inch mirror, may fail to provide adequate screen illumination because it is not optically correct; that is, it is not properly designed to coordinate with the new faster lenses. Most of the large-capacity lamps now in use suffer from this deficiency. Major Advances Claimed for New J NTRODUCiNG ncw pi’oduct developments for the attention of the trade is the expressed mission of The Cine Clinic. While your conductor cannot vouch for the correctness of all statements made concerning products introduced herein, we believe there is good point in allowing pn-oducers to describe their products in their own way. Clarence S. Ashcraft, designer and builder tf the new Ashcraft C-70 projection arc lamp, has the following to say concerning his new product, illustrations of which are shown and referred to in his description, which follows: “Three years in the planning and actual design stage, and marking thirty years’ experience in the building of cai’bon-arc lamps, the new Ashcraft Suprex C-70 (Fig. 1) projection lamp embodies several major features and numerous others which constitute a radical departure from conventional design. Among the important features of the C-70 are: “Wide range — 40 to 65 amperes capacity; unit construction — a compact removable mechanical element which simplifies operation and servicing and assures long life; exterior controls — all mechanical and manual controls are outside the lamphouse itself; dual feeding means — both positive and negative carbons are fed independently of each other by separate feed screws. “Optical system — so designed for a 14 Fig. 1. Exterior view of Ashcraft C-70 lamp, show compact grouping of all mechanical and control ports in a single element wholly outside the housing. Saprex C-70 Arc Lamp Fig. 2. Interior view of C-70 lamp showing 14inch reflector, arc alignment, arc stabilizer, door baffles and drip cup. inch mirror as to match perfectly an F:2 coated lens; modern housing — solid cast aluminum instead of the conventional sheet metal; novel control panel — all manual controls and an ammeter on a compact panel of high visibility at the rear operating side of the lamp. “Unique arc stabilizer — a simple yet positive-acting steel loop replaces the customary behind-the-reflector magnet; arc imager — visible from any viewing angle; precise carbon positioning — both vertical and horizontal negative alignment provided; non-slip duplex clutch eliminates pawls and ratchets, locking positively after each feeding cycle; non-wearing, non-oiling shafts, full ball roller and self-oiling bearings throughout; uncluttered lamphouse. no rods, pans, wires, etc. A carbondrip cup lifts out for cleaning. “The constantly increasing number of color films poses a serious problem in screen illumination for even the smallest theatres. Prevalent lamps are becoming obsolete for this reason, since they have limited range (40-42 amps.), an inefficient optical system (not adaptable for the fast P:2 lens), and a single nonvariable-ratio feed screw which defies even constant manual adjustment by the projectionist. “Single-feed-screw lamps have long been discredited by the exhibitor because of their constantly varying quantity and quality of light, and by the projectionist for the same reason, plus the necessity for “The primary requisite for any Suprextype lamp, irrespective of current capacity, and because of the critical nature of this type of arc, is the combination of precise control of both negative and positive carbons (possibly only by a dual feed means) and a highly efficient optical system. This combination must be provided for in the design and built into a lamp; there can be no revamping of the elements after the lamp is built. “It is this blending of hairline arc control and fine optical system, complementing the control inherent in its design, that enables the Ashcraft C-70 to encompass the wide current operating range it does. From 40 to 65 amps, and at all intermediate levels, control units and optical system work as a team to produce fine projection. "It is fallacious to utilize a fast lens of the order of F:2 or better with a lamp, the optical system of which is F;2.3, F:2.5, or F:2.8, which is the range covered by most lamps now in operation. The speed of the slower unit, whether lens or mirror, determines the over-all optical efficiency of a lamp. A hybrid combination of fast lens and slow mirror, or vice versa, is not efficient. “No mechanical changes are required on the C-70 lamp to effect the transition from the lowest to the highest current levels (40 to 65 amps.). Using an 8mm x 7mm Suprex carbon trim at 65 amps., the C-70 not only enables an optical speed of F;1.9, but compares favorably, in quantity and quality of light output, with a straight high-intensity lamp using 13.6mm carbons and pulling 126-130 amps. Considering the steadily increasing number of color film releases, no exhibitor, irrespective of how small a screen area he utilizes, can afford CLUTCH PLATE FEEDING CLUTCH ADJUSTING TENSION SPRING IN6 CLUTCH Fig. 3. New Duplex negative carbon feed clutch affords hairline control and renders slippage impossible. 48 The MODERN THEATRE SECTION