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Need Binoculars, This Info Will Help You Pick the Right One.

Updated on December 17, 2017

It’s time to buy binoculars. You go on-line or to your favorite sporting store. What do you find? Binoculars, some are large and powerful, others are compact with zoom focus features. They have coated lens, rubber armor. There are porro and roof prism styles, and they all have different sets of numbers, 7x35, 8x40, 8x22, and 10x50. What’s it all mean? Which pair of binoculars should you buy? Getting the right set can make birding a rich and rewarding hobby, buy the wrong set and you end up frustrated. A little understanding goes a long way and just might save you some money. Let’s talk about the basics and what they mean.

Magnification or Power

It seems that bigger is better, but this is not always true. Binoculars are broken down by a set of numbers, i.e.; 7x35, 8x40 12x60 and so on. The first of these numbers are the power or magnification number. This is how many times closer your subject appears. Your subject, being viewed by 7x35 binoculars will appear to be 7 times closer, the 8x40, 8 times closer. If you have 7 power binoculars and your subject is 70 feet away your subject will appear to be 10 feet away. It would only seem natural that you would want the most powerful binoculars available, a 12, or 14 power. You would be wasting your money.

Most birders use 7, 8 or 10 power binoculars, if you want to go higher than a 10 power you should think about using a spotting scope.

Why wouldn’t you want the most power available?

1. The higher the power or magnification, the narrower the field of view making it difficult to pick up birds flying or moving on the ground or in trees.

2. The higher the magnification the harder it is to hold binoculars still causing a lot more jiggle.

3. Image brightness is lowered with higher magnification, and a brighter image is very helpful in low light situations such as forested areas or at dusk and dawn.

Aperture or Objective Lens Diameter

The Aperture or Objective Lens is where light enters the binocular. This is the second number which is the diameter of the objective lens in millimeters. An example, 7x35, 35 is the size of the front opening or objective lens. So why not opt for the biggest lens available? Bigger than a #50 means bulker and heavier and might be great when sitting on the back porch, but it’s not so cool when it’s hanging around your neck while in the field for an extended period of time. Go for an objective lens number somewhere between 30 and 50.

Compact binoculars usually have an objective lens number of 20 to 25, or less. That’s fine for compacts, but they will not perform like full size binoculars. Don’t choose compacts if they are going to be your only pair of binoculars. I personally think binoculars close to 8x40 might be the best binoculars for bird watching.

Exit Pupil

The exit pupil is the diameter of light in millimeters visible through the eyepiece. For general purpose birding, choose binoculars with an exit pupil size of at least 4mm. If you do most of your birding in shaded forests, dusk or dawn, or on a moving platform (boat) choose 5mm or more.


Prism Design

Porro Prism Binoculars have a Z – shaped optical path where the objective lenses are offset from the eyepieces, resulting in a wider set of binoculars.

Porro prism binoculars are bigger and bulker, but provide a wider field of view and the offset lenses provide greater depth perception with more light gathering capacity for a brighter image.  The two offset prisms mounted separately are more susceptible to alignment problems if dropped and is a weaker design, but you can get a better quality binocular for less money with this design.

Roof Prism Binoculars have the prisms overlap closely and the objective lenses are almost in-line with the eyepieces.  The result is a slim, streamlined shape.

Roof prism binoculars are slim, streamlined, and lightweight.  The prisms overlap closely giving a smaller field of view and straight inline barrels decrease depth perception.  With proper lens coating Roof Prism binoculars can equal the light gathering quality of Porro Prism binoculars.  The cost to buy a Roof Prism binocular that equals the viewing quality of a Porro Prism binocular is higher.


Close focus is the shortest distance that your binoculars are capable of providing a sharp image.   As magnification increases, the close focal distance also increases.   There are times that you will want to study the details of birds that are 10 to 15 feet away.   A good birding binocular should have a minimum close focus of 15 feet, 10 feet would be better.

Ease of focusing is important.  Be sure you get binoculars with a central focus that can be comfortably turned with your index finger. Some models have individual focus eyepieces, these can be awkward and time consuming and if at all possible should be avoided.

Lens Coatings

Lens coatings increase light transmission and improving image brightness.  Lens coatings  effectively lower reflection losses resulting in a brighter and sharper image.  For roof prisms, anti-phase shifting coatings (p-coatings) are sometimes used and significantly enhance resolution and contrast.

The presence of a coating is usually denoted by the following terms;

·         Coated (C) -------------------- A single layer on at least one lens surface

·         Fully Coated (FC) ------------ A single layer on all air-to-glass surfaces

·         Multi-coated (MC) ---------- Multiple layers on at least one lens surface

·         Fully Multi-coated (FMC)---Multiple layers on all air-to-glass surfaces

More coatings, more cost, but better images, you will have to decide.


Weight distribution, or balance of binoculars may be more important than weight alone.  A poorly balanced 25oz binocular may cause more fatigue than a well-balanced 32oz pair.  The balance affects the feel in your hands, and over a long day, this may be a fatiguing factor.  Your hands, wrists and/or arms may notice the difference.  As a rule of thumb, for long days of birding, choose a binocular that weighs less than 30oz.


Waterproofing is a great option.  Waterproof seals are made with rubber O-rings and nitrogen gas purging.  Waterproofing  provides protection against water, dust, dirt as well as internal fogging.  Taking  warm binoculars out on a chilly morning without nitrogen gas-filled optics, will most likely cause fog-up on the interior.  If you’re in the field with rain, snow, humid climates or the possibility of dropping your binoculars while crossing a creek, waterproofing is a smart option.    

 Rubber Armoring

 Rubber armoring is not waterproofing.  Rubber armoring protects your binoculars from bumps, scratches, and corrosion.  It also provides a comfortable cushioned gripping  surface.  This option will add to the cost and weight of your binoculars.  It is a nice option, but once again, you must make this decision.



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    • StephenSMcmillan profile image

      StephenSMcmillan 6 years ago

      It is really great to learn something new about binoculars! Thanks for the info.