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1949 TELEVISION STUDIO LIGHTING 617
units can be brought to bear on a scene, they provide all the basic flat illumination required in an area 20 feet wide by 10 feet high. And they do this with a power consumption of only 450 watts per unit, a very efficient illumination.
Compare this effectiveness with incandescent lights. Fig. 1 shows spectral curves for a 4500-degree fluorescent and a 3000-degree incandescent. When filters are used to correct color response, watt for watt, the fluorescent produces about 21/z times more signal than the incandescent.
As previously suggested a combination of fluorescent with incandescent lamps furnishes a well-balanced spectrum for use with the typical television camera tube. Since the fluorescents are not seriously deficient in reds (assuming no filters on the camera) not a very large proportion of incandescent illumination is required to provide the balance. The requirements as to directive light for artistic effects are usually sufficient as to color also. Limiting usage of incandescent lighting to these requirements cuts down the heat dissipated in the studio and reduces the requirements as to cooling equipment.
Fig. 3 is an incandescent fixture equipped with internal reflector bulbs. This type of light is efficient for an incandescent because with relatively inexpensive facilities it achieves quite good directivity. The degree of concentration achieved with this 12-lamp unit provides a very intense beam as may be seen. Hence, it can be operated a little farther from the scene than the fluorescent and its greater intensity overrides the basic light of the fluorescent enough to give the desired character of high lights and shadows.
It is good practice to use bulbs in these units at a voltage higher than their rating; for instance a 105volt bulb on a 115-volt source. This shortens the life of the bulbs, to be sure, but it increases the radiation in the blue end of the spectrum and thus increases the effectiveness so far as the television camera is concerned.
Of course, the power used by this bank of lights is considerably in excess of that of a fluorescent unit: 1800 watts when equipped with 150-watt bulbs. This produces considerable heat which is unavoidable. A balance of 1 or 2 of these banks to each fluorescent provides good color response and sufficient directive illumination for most artistic effects. Where more sharply beamed illumination is required an incandescent spotlight may be used, but it should be equipped with a high-temperature-type bulb.