International projectionist (Jan-Dec 1936)

AN INQUIRY INTO THE KNEISLEY L. I. LAMP CONVERSION' PROCESS Substitution of Larger Reflectors No Guarantee of Increased Scree n Light Foreword: The Kneisley Electric Co., of Toledo, Ohio, advertises in the general trade press, by direct mail and through its representatives that its "conversion process" will increase the light output of a low-intensity lamp from 58% to 72% (and more in some instances) — at a cost of about 130 per lamp. The "Kneisley Process," it appears from the advertising, involves the substitution of 10%-inch reflectors for the 8-inch reflectors used in the early models of low-intensity lamps. A representative Kneisley advertisement is quoted here: "10%" REFLECTORS FOR LOW-INTENSITY LAMPS Strong-Motiograph-Brenkert-Powerlite-Peerless We're telling you that you have been throwing away 50% of all the light you have been paying to generate. 10%" Reflectors will give you 50 to 60% more light without increasing your operating costs one penny; 80% more light if you use SRA Carbons at 30 amperes. Carbon Arc Average Comb. Amperage Screen 7 & 10 mm. 18 18 ft. 8 & 12 mm. 25 18 ft. 8 & 12 SRA 30 18 ft. Reflectors by BAUSCH & LOMB Screen Illumination 7% or 8 in. Refl. 10% in. Refl. 7 ft.-cdls. 10.5 ft.-cdls. 8 ft.-cdls. 12.5 ft.-cdls. 9 ft.-cdls. 15 ft.-cdls. Equipment by KNEISLEY ELECTRIC CO." Installation instructions for this process state that the reflectors are the finest available, being made by Bausch & Lomb, to whom "complaints" will be referred to assure customer satisfaction. Numerous inquiries anent this process having been received from the field, LP. invited Mr. Kneisley to explain the procedure in a contribution to these columns. Appended hereto is his contribution; and immediately following is a discussion of the various interesting points raised by Mr. Kneisley. — Editor. By R. F. KNEISLEY THE increases in light given in our advertising matter (see sample in foreword to this article — Ed.) are given in percentages and represent results obtained through actual measurement in the field. Various results are obtained with different lamphouses, naturally, depending upon the reflector size that the theatre is using. We base our advertising on results obtained by photometric readings, and generalize a theory thereafter. This theory is readily understood, we believe, when considered from the standpoint of reflector area rather than diameter. The 7%-inch reflector, as used in the Peerless low-intensity lamp, has a total area of approximately 46 square inches; whereas a lO^-inch reflector has a total area of 83 square inches — an increase in area over the smaller reflector of approximately 80%. Total Light Increase of 72% In a polar curve taken in a conical position around the arc, it will readily be observed that useful light in large quantities is available through the included angle of 145 degrees. The 10%inch reflectors have a light angle of 132 degrees, as compared with the angle of 90 degrees of the 7%-inch reflector. If the distribution curve was uniform throughout its entire length, theoretically there would be present an increase of 80% in reflected light, as a result of substituting the larger reflector. However, since the distribution curve tapers at its extremities, the actual light increase brought about by the increased reflector diameter (of the 10%-inch mirror) is 58%. By removing the condensing lens necessary in Peerless lamps, a light increase of 14% is realized, since there is a 7% light loss through each change of medium (two, in this case) through which the projected light must pass. This 14%, added to the 58% gained through increased reflector area, makes a total gain of 72% in screen illumination. This figure can be increased to 80% through employment of SRA carbons at 30 to 32 amperes, which set-up is optional. The same results are obtained in the, case of larger reflectors, i. e., the change from 8-inch to 10%-inch reflectors will increase the projected light by about 56%, using 8 x 12 regular carbons, and to about 70% when 8 x 12 SRA carbons are used. The figure of 72% is the maximum gain claimed by us. Very conclusive proof of the merits of this process is available from either the Sparks-Publix or the Warner Theatres circuits, which are installing 10%-inch reflectors in all their low-intensity lamps. Since the first of the year we have distributed more than 2,600 reflector equipments. Actual measurements made at the Plaza Theatre, Sandusky, showed an actual increase in light of 72%, as measured by a Weston Photronic FootCandle Meter. Installation Instructions [Excerpts from the installation instructions issued by the Kneisley Co., which may help to further explain this process, are appended hereto : "Take the bakelite knob from the old screws and place them on the special milled shaft. This will enable you to burn the carbons very short ... In extreme cases use the special nose castings, particularly where you are using very long focal length lenses. Any light striking the FIGURE Magnification is 24:4 — 6; speed is 24:8 — f/3 [20]