How to Choose Binoculars

This is a work in progress.  Please check back soon, we are updating this regularly.

Welcome to the wonderful world of binoculars.  Whether you're exploring the night sky, seeking out interesting nature, taking in an event, or require some assisted vision, binoculars are an excellent tool that no observer should be without.

Binoculars are available with a wide variety of specifications, suitable for a wide variety of activities.  Selecting the optimal pair is crucial to your enjoyment.  Let's jump right into the specifications.

8x42

Magnification

In the above example, 8x is the magnification factor; how large do objects appear in the binocular.

Your first thought is probably that a bigger first number is better, right?  The answer depends on a number of factors.

  • the ability to hold the binocular steady
  • field of view requirements
  • brightness requirements

In addition to making objects appear larger, magnification also enlarges the user's movements.  Some people are steadier than others and can use higher magnifications, but eventually a magnification will be reached where the image becomes unstable.

People often select binoculars while at rest, but what if you're active?  During a long walk, with your heart pumping and adrenaline coursing through your body, that binocular your carefully selected suddenly produces a jiggly image that's difficult for your eyes to track.  Your activity level should also dictate the magnification you chose.

One way to avoid the jiggles with high-powered binoculars is to mount them to a tripod.  Virtually all decent models on the market today are tripod-mountable.  Electronic image stabilized binoculars also exist for when a tripod is too cumbersome.

Magnification also affects brightness.  The lower the magnification, the more concentrated the light is, resulting in a brighter image.  Conversely, the higher the magnification, the more spread-out the light becomes, leading to a dimmer image.

 

Objective

Referring back to the above example, the second number represents the diameter of the objective lens in millimetres, which is the lens closest to the object you wish to observe.

The objective lens plays three crucial roles:

  • light gathering
  • resolution
  • overall physical size of the binocular

Larger objective lenses collect more light, leading to a brighter image.  Resolution is improved, so you can discern finer details in the image.

 

7.4°     388ft @ 1000yds

Field of View

The field of view represents how wide you can see.  Wider fields of view are often more advantageous, as it makes locating subjects easier with less aiming around, and let you see more of the action.

Field of view is expressed in one of three measurements.

  • Degrees
  • Feet of width at 1000 yards distance
  • Metres of width at 1000 metres distance

Degrees tends to be easier to visualize.

You can convert degrees to ft@1000yds simply by multiplying the degrees by 52.5, since 1 degree = 52.5ft@1000yds.

Or convert degrees to m@1000m simply by multiplying the degrees by 17.45, since 1 degree = 17.45ft@1000yds.

Just because a binocular shows a wide field of view doesn't mean the entire image will be sharp and low in distortion.  Often the opposite is true, unless the manufacturer put a lot of effort into correcting field.  A perfect example of this is the Swarovski NL Pure series of binoculars, which have outstanding sharpness, aberration and distortion control.

 

More to come.  Check back soon.