Understanding Digital Camera Zoom Lenses

Photo by Pixeleye

By Michael Huddleston

There are two types of zooms used with digital cameras: optical and digital.

Optical Zoom
An optical zoom changes magnification by moving glass in the lens, changing the image falling on the sensor. Using an optical zoom maintains picture quality.

Zoom Ranges and 35mm Equivalents
Optical zoom lenses usually have a specification called “equivalent in 35mm.” This tells you the zoom range of the digital camera compared to a 35mm film camera. Typical 35mm equivalent zoom ranges you will see listed are 35mm-70mm or 35mm-105mm.

For example:

Wide-angle means a lens takes in more than normal viewing perspective. Telephoto lenses magnify the subject, bring it closer. Using these numbers as a guide, you can get an idea of the range of zoom lenses and what they will do for you.

28mm…..wide angle
35mm……slight wide angle
50mm…..normal perspective
70mm…..slight telephoto
105mm…..moderate telephoto
135mm…..strong telephoto
200mm+…..extreme telephoto So, a 35mm-105mm equivalent zoom lens changes from a slight wide angle to a moderate telephoto. A 28mm-200mm equivalent lens changes from a wide angle to an extreme telephoto.
A 35mm-105mm equivalent zoom is adequate for most users. If you plan on doing landscapes or picture taking in small, confined areas, consider a camera that can zoom to a 28mm equivalent.

Optical Zoom as 2x, 3x, 5x…
Taking the 35mm-105mm example above, we divide 105 by 35 to get a 3x zoom. A 28mm-105mm would be approximately a 4x zoom, and a 35mm-350mm would be a 10x zoom.

Digital Zoom
A digital zoom does not change, magnification. It simply crops the image on the sensor to magnify the image. Because less sensor is used, you use fewer pixels. This decreases picture quality. When comparing cameras, always use the optical number as this is much more important. You can get the same effect as a digital zoom by using software to crop the photos.

Note About Digital Zoom
As digital cameras become more sophisticated and powerful they are becoming capable of delivering “optical tricks” that render pictures that are remarkably stable and good looking. Only recently, cameras “digital zooms” are getting much better. Like all things though some companies are better than others. Do your research.




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