Line of Sight Binoculars

Buying Guide

With the number of Binoculars you’ll find on our site, you might be asking yourself “which are the right Binoculars for me?”.   The details below are intended to help you understand the key components of binoculars, their size and also the preferred applications. We really hope this helps you in your buying decision. 

What Types of Binoculars Are There?


Common specs are usually 8 x 25 and 10 x 25.

These make a great choice of binocular for backpacking and any daytime activity You may find though that they’re less comfortable for extended periods of use.



Common specs are usually 7 x 35 and 10 x 32.

Mid-size will give you above average light transmission. This makes them popular for  both wildlife and sports use.  They are though a bit heavy  if you’re going to be backpacking.


Common specs are usually 8 x 42 and 10 x 50.

These perform better in low-light situations as they capture more light.  Perfect for serious wildlife viewing and for use on boats. Again probably too heavy to carry around all day.

What are the Common Binocular Specs?

Objective lens

This is the outermost lens, the one that is closest to the objects you are looking at. It is measured in millimeters, and the larger the objective lens, the more light the binoculars let in and the brighter the image will be.


The aperture tells you the magnification and the objective lens diameter; for example, 7×35 magnifies seven times and the objective lens has a 35 mm diameter. Any pair of binoculars should list the aperture in the product description.

Exit Pupils

The beams of light that exit the eyepieces and hit your pupils are called exit pupils; these help determine brightness: Larger exit pupils let in more light. Divide the diameter of the objective lens by the magnification to find the size. For nighttime use, you will want a larger exit pupil, around 7 mm.

Inter-pupil distance

This is the distance, in millimeters, between the two eyepieces. The distance between the average person’s pupils is between 60 mm and 72 mm. Make sure you choose binoculars that will adjust to your size. You can have someone measure the distance by looking straight forward and using a metric ruler.

Focusing Method

Many binoculars focus with a central knob to adjust both sides at one time; however, some binoculars have a fixed focus, also known as “focus free,” so they will not have a focusing knob. Others will have a diopter on one barrel of the binoculars, so you can customize the view through each eye.

Eye Relief

The eye relief is the distance between the eyepiece and the user’s eyes. Eyeglass wearers should choose a long eye relief, at least 13 mm. Some binoculars have an adjustable eye relief for multiple users, using methods such as rubber eyecups which fold back.