Journal of the Society of Motion Picture Engineers (1930-1949)

1949 TELEVISION STUDIO LIGHTING 623 knowing the position of those various units, arid we can determine from the knowledge we have of those particular types of lights exactly how many footcandles you build up in a certain area and what color coefficients you will achieve. We say, though, for rule of thumb in computing a television studio, that even though the incandescents are going to be farther back, they have more throwing power, and if your fluorescents are placed halfway in to the staging area two to one seems to be a reasonable standard in roughly estimating a studio. Before we came down with a final layout, we necessarily would have to see the height of the ceiling and the aspect ratio of the studio. MB. A. M. ZAREM: Have pulse-light sources ever been experimented with on television? CAPTAIN EDDY: Possibly, but not to my knowledge. Certainly our company, which has been in this lighting field, has not done anything along that line. We have experimented with mercury lights, various types of incandescents, and fluorescents and have arrived at something that appears to be satisfactory to us. However, I do not believe that television is going to stagnate on one lighting system when a new and better system is developed. When this happens, I believe it should be tested, but I know of no experimentation in pulse lighting at the present time. MR. HUNGERFORD: What power source do you use on those lights? Does that make much difference? CAPTAIN EDDY: That is a matter which has led to considerable controversy and some difficulties. One complete direct-current installation in a television studio led to magnetic fields which seriously affected the framing of the television picture. Alternating current is satisfactory for lighting but high-current conductors should not be placed close to the cameras as their fields may cause trouble. Use of alternating current for lighting does not cause hum bars to appear in the picture with either incandescent or fluorescent illuminants, but the lighting fixtures should be balanced on a 3-phase system wherever possible. Each one of these units I have shown you connects to two circuits. A threewire balanced system sometimes helps you cut down the amount of basic wiring needed. The reason why we have divided the units between two circuits is to permit half illumination during setups and rehearsals while maintaining the same distribution of illumination that would be obtained with full illumination. All light distribution problems can be worked out under half illumination and the balance of the lighting turned on only when needed. MR. EDWARD P. SUTHERLAND: Do you use 60-cycle single-phase power on the fluorescent lights? CAPTAIN EDDY: Yes, sir. MR. SUTHERLAND: Do you have that in phase with the generators at all? CAPTAIN EDDY: The single-phase alternating-current supply to the fluorescent lights is split into two phases in the ballast units connected to the fluorescent tubes. As a result of this, flicker is smoothed out to such an extent that hum bars are not produced in the television pictures. Consequently, phasing of these lamps with the synchronizing generator is not necessary. Since ordinarily both the lights and the synchronizing generator are supplied from the same source, there will be a fixed-phase relationship between them, but it is not a prerequisite to use the fluorescent lights.