Digital Camera Zoom

Digital Camera Lenses

Point-and-shoot zoom lenses
Most point-and-shoots today have zoom lenses, which are labeled in a couple of different ways. Sometimes you’ll see them both: For example, “3x optical” and “28mm-84mm film equivalent.” Both mean essentially the same thing, except that the latter figure is telling you what the zoom range would look like if you were looking through a film SLR camera. The technical reason is that the numbers on the zoom lens might actually be something like 8mm-27mm. But most people are more accustomed to understanding how lenses look on an old film SLR camera. So, we know that a 50mm lens on a film camera is more or less our normal field of vision. Anything higher, such as a 200mm lens, is considered a telephoto lens. And anything lower, such as a 24mm lens, is considered a wide-angle lens. So most manufacturers will include the terms “film SLR equivalent zoom” or “35mm equivalent.”

You might also sometimes see the term “digital zoom” in a point-and-shoot camera. Digital zoom works by cropping in on a portion of the image from the camera’s image sensor and magnifying it, or sometimes, interpolating it. When you use digital zoom, it always degrades the quality of the image. CR’s Take: Whenever you buy a digital camera, be sure to turn off the digital zoom in your camera’s menu.

SLR lenses
In our tests of SLR lenses, performance varied widely and bore no relation to price. Here are some considerations before you buy:

Assess your existing lens. If you already own an SLR, one of the rated zooms might be a step up from your lens. Among lower-priced zoom lenses, wide-angle models might offer better image quality than those that are more oriented toward telephoto (i.e. 200mm or 300mm).

Consider a wider zoom range. Most SLRs are bundled with a wide-angle zoom kit lens similar to those in the Ratings. But you can buy the body alone or together with a different, more versatile lens. If you think you might someday need a greater range than the standard kit lens offers, and your budget permits, buy the camera body bundled with a full-range zoom instead. You’ll dramatically expand your shooting options and what you save on the kit lens will partly offset the bigger lens’s higher cost.

Investigate camera compatibility. Different lenses mount to different brands of camera. Some utilize the four-thirds system, a universal mount used on some Olympus and Panasonic models, instead.

Look for non-zoom lenses. Those with a fixed focal length generally have higher image quality and light sensitivity than comparably priced zooms.

source: consumerreports.org