Autofocus, on the other hand, means the lens system is motorized, and it automatically adjusts itself to take the best photograph. An autofocus lens determines how far away an object is from the center of the camera's lens, and automatically adjusts its optics to lock onto the subject and bring it into sharp focus. Sometimes you may want an object in the foreground to be slightly blurred and the background to be in sharp focus. To achieve special effects like that, you'll want a camera with manual-focus capabilities. A telephoto or zoom lens lets you adjust how close or how far a subject appears in your picture.
Many cameras have optical zoom and digital zoom capabilities.
With digital zoom, the camera takes a part of the picture the lens captures, enlarges it, and throws away the rest. Compression shrinks the file size of a captured image down to a more manageable size, and most digital cameras use some kind of compression. This algorithm analyzes an image and throws out data that it thinks is nonessential to the picture. It doesn't throw away important details like buildings, people, or landscapes, but it does throw out the data that can't be perceived by human vision. The basic setting compresses an image to one-sixteenth its original size, useful for viewing only on a computer, and that would make a terrible print.