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In this section, we examine the following electronic characteristics of a television camera: l Operating light level l Video noise Operating Light Level You need a certain amount of light in order for the pickup tube of the camera to perform its function. Although there are several ways to measure light, the footcandle is one of the more common units of measurement. Whatever term is used, make sure your lightmeasuring device is in the same language as the manual for your camera. For example, if the manual calls for a minimum of 100 footcandles of light, you will need a light meter that reads in footcandles. Some cameras have a way to give you more light when you need it. The dB gain switch (fig. 14-3), usually located on the back of the camera, has two positions - 6dB and 12dB. For every 6dB of gain, the camera output
Figure 14-3. - Television camera dB gain switch. signal doubles in amplitude to increase the video level . effectively. That means the 6dB setting doubles signal strength and the 12dB setting is four times more than the 6dB gain. Video Noise Video noise increases in proportion to the video gain previously described. Even the best cameras will deliver "noisy" pictures under low-light levels. A noisy picture has a great amount of snow, or white vibrating spots, in the picture. This occurs when the video signals produced by the pickup tube are not strong enough to override the electronic interference the system usually generates. At 12dB gain, the system is generating more electronic interference - and more video noise. Having covered the basic operation and electronic characteristics of a video camera, we now examine the types of video cameras you will work with at NBS detachments. STUDIO CAMERA The studio camera (fig. 14-4) is the backbone of the television industry. It is mounted on a dolly pedestal so the camera operator may wheel it to different locations with relative ease during shot changes. Television technicians monitor and adjust the video levels of the studio camera with the camera control unit
Figure 14-4. - Studio camera.
Figure 14-5. - E1ectronic news gathering (ENG) camera. (CCU), usually located in the control room. The CCU consists of a waveform monitor (an oscilloscope that displays a video signal graphically), television monitor and shading control. Studio cameras are expensive, ranging in price from under $5,000 to more than $100,000. However, the more expensive cameras deliver high-quality images in a variety of production conditions. The electronic news gathering (ENG) video camera replaced 16mm motion-picture film for television news in the mid-1970s. The ENG cameras are automated and fully operational within a few seconds after they are switched on. You can make adjustments to extreme production situations quickly and easily. Most ENG cameras weigh between six and 20 pounds, depending on the number of pickup tubes inside the camera. They are powered by batteries, but you may also run them from AC current using an adapter. An ENG camera is shown in figure 14-5. |
 
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