For traditional cameras, the light-sensitive detector was film. Today’s digital cameras use a rectangular array of many millions of small light detectors called pixels. When light hits one of these pixels, it generates an electric charge proportional to the light intensity. Thus an image is recorded on the detector in terms of little packets of charge. After the image has been recorded, the charges are read out, the signal levels are digitized, and the picture is stored in the digital memory of the camera.

FIGURE 35.5a shows a detector “chip” and, schematically, the magnified appearance of the pixels on its surface. To record color information, different pixels are covered by red, green, or blue filters. A pixel covered by a green filter, for instance, records only the intensity of the green light hitting it. Later, the camera’s microprocessor interpolates nearby colors to give each pixel an overall true color. The pixels are so small—a few micrometers across—that the picture looks “smooth” even after some enlargement. Even so, as you can see in FIGURE 35.5b, sufficient magnification reveals the individual pixels.

FIGURE 35.5 The detector used in a digital camera.

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