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White balance is a function that tells the camera what the colour white looks like. This function helps calibrate the other colours in our video accurately (since white is essentially the combination of all colours). What the camera does when we perform the white balance is, it gets ready to record the picture in its true colours. When the white balance is incorrect, it shows different colours-sometimes bluish and sometimes orangish-yellow, see Figs 2.9(a), (b), and (c).
While consumer grade camcorders have an auto-white balance function, in professional cameras, the we need to perform the white balance function every time the lighting changes-at the start of the shoot early in the morning, at least once around 12 noon, again about 2.30 p.m., then 4.30 p.m.,
 
| and once again about 5.30 p.m. This is be¬cause the colour temperature changes with time (we shall learn more about colour temperatures in the chapter on lighting). The thumb rule is, perform the white balance every time the lighting conditions change, whether outdoors or indoors or when the nature of lighting changes¬ natural or artificial.
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How to perform manual white balance
Different lighting conditions warrant the performance of white balance. This becomes imperative particularly if we are moving from outdoors to indoors, when we begin to shoot with artificial lights. We should also perform white balance when we shift from indoor location to another location lit by different kinds of lights.
To perform white balance, you will need a camera with a white balance function and a white sheet that is not shining (the thermocol sheet used as a reflector will do). If the camera has different in-built filters for different lighting conditions (bigger camera models do; most ENG cameras do not), use the correct filter. Point the camera to the white sheet and make sure the entire viewfinder is covered with the white surface (Fig. 2.10). Set the exposure and focus properly. Now activate the white balance button. In the viewfinder, you will find the picture changing for a couple of seconds. In most cases, the camera 'informs' you that the white balance has been performed. Even otherwise, the picture in the viewfinder (or LCD panel) will show that the white balance has been performed. You are now ready to shoot.
Some professional cameras also come with a black balance button. This function is similar to the white balance except that the black balance gives reference to true blacks in the picture. While some camerapersons feel it is necessary to perform the black balance· every time the white balance is performed, some do not bother to do it. However, if the camera has a black balance facility, it serves well to perform the black balance after the white balance every time lighting conditions change significantly.
If your camera has a black balance button, close the iris first and cover the lens with the lens hood. Then press the black balance. Now open the iris as required. Some camera persons follow the white-black-white balance sequence to be doubly sure.
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