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Many compact digital cameras can perform both an optical and a digital zoom. A camera performs an optical zoom by moving the zoom lens so that it increases the magnification of light before it even reaches the digital sensor. In contrast, a
digital zoom degrades quality by simply interpolating the image-- after it has been acquired at the sensor.Even though the photo with digital zoom contains the same number of pixels, the detail is clearly far less than with optical zoom. Digital zoom should be almost entirely avoided, unless it helps to visualize a distant object on your camera's LCD preview screen. Alternatively, if you regularly shoot in JPEG and plan on cropping and enlarging the photo afterwards, digital zoom at least has the benefit of performing the interpolation before any compression artifacts set in. If you find you are needing digital zoom too frequently, purchase a teleconverter add-on, or better yet: a lens with a longer focal length.