December 9, 2010

Binoculars (III/V) – diameter

There are four important numbers associated with any pair of binoculars: magnification, diameter, field of view, and price.

The second number “50” written on a pair of binoculars is the diameter of the objective lens. This number is more physics than practicality but in a nut shell the larger the diameter the more light enters the binocular producing a crisper, brighter image. For a more in depth description click here. Most bird watching binoculars run 30-50mm. The downside of a larger diameter is heavier, often more expensive binoculars.

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is an educator, bird watcher, and writer fascinated by the intersections of place, people, nature, and culture. He works for Mass Audubon and lives in the heart of Massachusetts. For questions or comments please contact:

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