Digital Photography: The Missing Manual

Deciphering Optical and Digital Zoom

In digital camera ads (or even on the camera itself) you see announcements like: “3X/10X ZOOM!” The number before the slash tells you how many times the camera’s lens can magnify a distant image, exactly like binoculars and telescopes. That measurement is called optical zoom.

Then there’s the number after the slash—the digital zoom. Camera boxes often announce digital zoom stats in big, gaudy type, as though that’s all their customers care about. Well, those are the same kind of people who buy into the notion that a higher megahertz rating always gets them a faster computer.

Truth is, digital zoom is nothing to write home about. When a camera’s digital zoom kicks in, the camera’s merely spreading out the individual pixels, in effect enlarging the picture. The image gets bigger, but the picture’s quality deteriorates. In most cases, you’re best off avoiding digital zoom altogether.

Tip

If you’re used to traditional photography, you may need some help converting digicam optical zoom units (3X, 4X, and so on) into standard focal ranges. It breaks down like this: A typical 3X zoom goes from 6.5mm (wide angle) to 19.5mm (telephoto). That would be about the same as a 38mm to 105mm zoom lens on a 35mm film camera.