The Bayer matrix

Almost all digital cameras sense color by using a Bayer matrix of filters in front of individual pixels (Figure 2.4). This system was invented by Dr. Bryce Bayer, of Kodak, in 1975.3 Green pixels outnumber red and blue because the eye is more sensitive to fine detail in the middle part of the spectrum. Brightness and color are calculated by combining readings from red, green, and blue pixels.

At first sight, this would seem to be a terrible loss of resolution. It looks as if the pixels on the sensor are being combined, three or four to one, to make the finished, full-color image. How is it, then, that a 6-megapixel sensor yields a 6-megapixel image rather than a 2-megapixel one? Is it really as sharp as the number of pixels would indicate?

3 Pronounced BY-er, as in German, not BAY-er.

For the answer, consider the dots in Figure 2.4 (right). Each dot represents a point where pixels of all three colors come together, so the brightness and color at that point can be determined exactly. The dots are "virtual pixels" and are as closely spaced as the real pixels.

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