Tuesday, May 24, 2011

What do the numbers in a binocular name mean?


The numbers on a binocular describe its configuration. Let's take 8x42 binoculars as an example. The first number (8) refers to the magnification, or, how many times closer an object will appear when looking through the binocular compared to looking at the same object with the naked eye. The second number (42) indicates the diameter of the objective lens (the light-gathering lens) in millimeters.

Consider this general rule about optics: low magnification provides a wide field of view and is easy to hold steady. So although a magnification of 10, 12 or higher is available, 6, 7, and 8-power binoculars are easier to use and in many cases more practical. For a better understanding of this, please see our short video, Understanding Optics: Magnification.

In regard to the objective (front) lens size: the bigger the lens, the heavier the binocular. While a large lens may provide a brighter image (all other things being equal), the compromise is increased size and weight. On the other hand, a compact binocular fits in your pocket quite nicely, but because of its small objective lens size, it will not be as bright, especially in low light conditions such as dawn, dusk, or in the woods. Our video, Understanding Binoculars: Aperture, will help illustrate this.


  1. i have some binoculars 12x50 262f.at 1000yrds.
    Can you please tell me more about them and price as they come with an old case. I was told they are very valuable.
    Thanks victoria

  2. Hi Victoria,

    What brand are they?

    Mike M.
    Eagle Optics

  3. Hi Mike,
    Thanks for your reply.
    Iv looked at the Binoculars and there is no brand name on them.It has got japan jb207 on the binoculars.
    Also on the bottom of the case on the outside it has japan.
    thanks victoria

  4. Hi Victoria,

    I can't really give you a value without knowing what brand and model they are.


    Mike M.
    Eagle Optics


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