The practice of reporting the photometric performance of the ellipsoidal-reflector spotlight

In 1957, a joint committee of the Illuminating Engineering Society and the Society of Motion Picture and Television Engineers published the "Recommended Practice for Reporting Photometric Performance of Incandescent Filament Lighting Units Used in Theatre and Television Production." The objective of this publication was to standardize the manner in which photometric information was to be reported on lighting manufacturers' instrument data sheets. In 1958, this "Recommended Practice" was adopted as an industry standard by the United States Institute for Theatre Technology and the American Educational Theatre Association. The "Recommended Practice" establishes a guideline to be followed in the testing of lighting units, and it presents a very definite example of how the photometric performance specifications derived from this testing are to be presented on manufacturers' data sheets. If each lighting manufacturer followed this practice, a customer might easily compare the data sheets compiled by one manufacturer to those compiled by another manufacturer and therefore determine which lighting unit would best suit his needs. This is not the case, however. In the twenty years since the "Recommended Practice" was published, lighting manufacturers have developed their own testing procedures, and each has produced its own version of photometric data sheets. The direct comparison of lighting unit specifications from one manufacturer to those from another manufacturer is made very difficult if not impossible. From the companies in the United States which produce lighting equipment, three were selected for the purpose of having their data sheets examined. Those companies were the Altman Stage Lighting Company, the Kliegl Brothers Universal Electrical Stage Lighting Company, and Berkey Colortran. Each of these companies has designed its own version of the ellipsoidal-reflector spotlight and manufactures the units it sells. Each company has tested or has had tested its line of instruments and has made the results of these tests available to customers on their respective photometric data sheets. It was the purpose of this study to present and define the reporting standards as established by the IES/SMPTE "Recommended Practice" and then compare these standards to the current data reporting practices demonstrated by Altman, Kliegl, and Berkey Colortran. The testing and reporting procedures examined have been limited to those which pertain to the ellipsoidal-reflector spotlight. A detailed examination has been made of those sections in the "Recommended Practice" which relate to the ellipsoidal-reflector spotlight, and each of the selected companies' methods of ascertaining and reporting photometric data on those lighting units has been analyzed.