Digital Versus Optical Zoom

Most digital cameras have optical zoom lenses that allow you to vary the focal length and subsequently change the size of an image as it’s captured on the imaging chip. In advertising, zoom lenses are often described by the ratio of their longest to shortest focal lengths A zoom lens with focal lengths ranging from 100-400 mm can be described as a 4:1 or alternatively 4X zoom, which I dislike because it ignores starting and ending focal lengths that I think are more important that just the ratio.

Some digicams offer a feature called digital zoom that is produced by cropping the captured image in-camera and then interpolating it to emulate the maximum resolution, in effect emulating a longer focal length. This process always produces a lower quality photo than that what would normally be captured with an optical zoom lens because you are tossing away image resolution.

Riddle me this: Was this classic car cropped or was it photographed with a digital zoom and does it even matter? ©2011 Joe Farace

You can achieve the same effect as a digital zoom by cropping the original file with even the least expensive image-editing program, so what’s the big deal about digital zoom? It’s all about marketing not photography, so don’t be fooled when the manufacturer erroneously combines the ratios of both optical and digital zooms giving you double the amount of worthless information.

Answer: It was cropped from the original photograph after the fact. ©2011 Joe Farace

Author: Joe Farace

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