One limiting factor is the viewing Angle, which is comparable to using a camera lens: a telephoto lens has a narrower view than a wide-angle lens.

限制因素之一就是观察角度，这与使用照相机的情况类似：长焦镜头的视野比广角镜头的观察角度要窄得多。

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Then there is the camera, the telephoto lens, and the cellphone with a camera.

然后就是相机、长焦镜头、带摄像头的手机。

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For example, Nikon's $399.95 P500 offers a 36x zoom -- the equivalent of an 810 mm telephoto on a 35 mm camera -- but easily fits in a laptop bag.

比如，尼康售价399.95美元的P500可以变焦36倍——相当于在35毫米相机上装一个800毫米的长焦镜头——还能够轻而易举地放入手提包里。

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It's lazy man's game viewing at its best, although you do go farther afield on game drives, where you're armed with a Canon 40D digital camera and a pair of telephoto lenses, about the coolest game-lodge amenity I've ever come across.

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As a result, the PENTAX Q10 produces sharp, blur-free images even under demanding conditions that are prone to camera shake, such as use with a telephoto lens or shooting in low-light without flash.

ENGADGET: Pentax offers 100 different custom color options for its Q10 mirrorless camera

This hybrid system guarantees the photographer sharp, blur-free images even under demanding shooting conditions prone to camera shake, such as when using a telephoto lens, shooting with incident light in poorly lit locations, or photographing sunset scenes.

ENGADGET: Pentax launches brass-bodied MX-1 point-and-shoot: 12MP with 4X zoom (update: now with hands-on photos)