30 sec. 1 min. 1 min. 30 sec. 2 min. Time from switch-on

30 sec. 1 min. 1 min. 30 sec. 2 min. Time from switch-on

Figure 28. Transient characteristics of lamp from switch-on.

acteristics of the HMI and CSI types, but precautions regarding flicker must still be observed.

Filters for adjusting the spectral energy distribution of CID lamps are listed on pages 366-367.

Light-Source Filters

These light sources vary not only in color temperature, but there are likely to be significant green-magenta shifts. It is recommended that anyone regularly working with the types of AC arc discharge sources delineated above should have a three-color color temperature meter. With such an instrument, and the system of filters created by Rosco Laboratories, Inc., it is possible to deal properly with all of the variations that are likely to be encountered with these lamps.

The possible range of lamp-to-lamp variations in color balance is primarily due to aging and manufacturing variations. In many situations, it will be highly desirable or essential to assure that the lamps in use will have the same color rendering characteristics.

Some claims have been made for single conversion filters for the HMI and CSI type lamps, but it is difficult to understand how a single filter could even come close to meeting the wide range of possible lamp color balances that are likely to be encountered within a given type. The range of available materials has been proven in practice to meet the requirements of color balancing lights so that minimum variations are present.

High-Pressure DC Short Arc Xenon Light Sources

This source is the best commercially available light source for use in higher-powered projection systems. The very small size and very high brightness of the arc source, and the stability of the arc location due to the DC operation, make it the source of choice around the world for motion-picture projection.

The efficacy of high-pressure xenon sources (lumens/ watt) ranges from 35 to 50 LPW. Ballasting is very simple,

CAUTION: These lamps have high internal pressure even when cold. They are supplied with a protective jacket over the bulb, and this should not be removed until the lamp is fully installed. It is required that a suitable face shield, body jacket and gauntlets be used any time that the protective jacket is removed. When removing a lamp the protective jacket should be installed before steps are taken to disconnect and remove the lamp.

requiring only a current-limiting rectifier that can produce DC that has less than 5% ripple. A high-voltage igniter is necessary to start these lamps, and they can be hot re-struck. These lamps permit the creation of an intense focused beam of pure, slightly cold daylight color balance light (about 6000° K), and have a Color Rendering Index of 95 to 98. They have found some limited application in motion-picture photographic lighting. The source is available in a wide variety of wattages up to 10KW.

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