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What’s All This Light “Temperature” Stuff?

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May 15, 2009 by admin

In digital imaging there is a fundamental practice all videographers must contend with–White Balance. Without an initial white balance, white will not be white and an overall hue will pervade the picture. To obtain a white balance the videographer places a white source in front of the camera and then tells the camera that what it is currently looking at is white.

The astute reader is probably now asking, “Why isn’t white always white? What’s the big deal?” Here is another example of why human imaging capabilities far surpass electronic imaging technology of today. Suppose you were to look at a white table cloth in a dance lounge where the DJ had a lot of multi-colored lighting flooding the dance floor. Would the white table cloth still look white to you? Probably not. The exact same limitation exists for electronic imaging except that it is far more narrow. Outdoor light is a different color or temperature than indoor tungsten light. The human brain is able to process the difference and white still looks white to you whether you are outside or indoors. Electronic imaging technology has not come that far yet. Recent technology developments have enabled an auto white balance capability commonly used in consumer grade cameras which is not too bad at white balancing. However, the pro videographer cannot settle for such white balancing and usually will want to manually capture a white balance before each shot.

There are two fundamental conditions that are commonly light balanced for: outdoor and indoor. While each has variations within, generally speaking outdoor light is 5700K (degrees Kelvin) and indoor tungsten lighting is 3200K. With a camera white balanced for outdoor imaging white will have a yellow hue when captured indoors. An indoor white balanced camera will show white outdoors with a bluish hue.


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