Choosing Binoculars

Binoculars are simple to use but can have different viewing results and purposes through varying features such as the objective lens, angle-of-view, prism design and eye relief.  Your understanding of these features and the way to combine them to your specific need will help you identify the pair that is right for you.   

What do the figures mean?

An example highlights this best: 8 x 21.  The first number (8) represents the magnification power - in this case, 8 times larger than viewed with the naked eye.  The second number (21) represents the diameter (in millimeters) of the objective lens - in this case, 21mm. The objective lens is closest to the object you are viewing (not the lens near your eye) and is a good indicator of how much light the binoculars can gather.   

What is angle-of-view?

The angle-of-view represents the portion of a circle you can view through a binocular. Since direct comparison of the angle-of-view between binoculars with different magnifications can be misleading, you can calculate the apparent angle-of-view by simply multiplying the binoculars' real angle-of-view by the magnification. An apparent angle-of-view of 65 degrees or more is considered wide-angle, which makes it easy to track moving objects and is therefore ideal for viewing wildlife and sporting events.

Prisms Designs.

Prism design is mostly a matter of preference. Roof prism binoculars have a slim, straight profile and are more compact. They are often more expensive because their smaller prisms require more precise lens grinding and polishing to achieve excellent image quality. Porro prism binoculars are recognized by their offset lens barrel design. As a result of the design, the wider spacing of their objective lenses enhances perspective to produce a more realistic, three-dimensional image.

Anything Else?

Look for multi-coated lenses if you will using the binoculars alot at twilight or night.  Coated lenses enhance the capability to transmit available light.   

Eye relief refers to the maximum distance from the eyepiece lens at which the entire image can be seen.   Look for binoculars with 13mm or more of eye relief if you wear glasses.