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Choosing a binoculars - beware the ‘power’ hype!

Author: admin
Filed under: Buyer's Tips, binoculars
Date: Apr 7,2008

Basic Binocular Components:

Objective Lenses: The ‘front’ lenses collect light, and therefore enable high-resolution observation of distant objects

Prisms: Since the objectives form images that as upside down mirror-images, special prisms are used inside the binoculars to invert the image so that you see it in its correct orientation.

Eyepieces: The main function is to magnify the image formed by the objective lens.

Main considerations

required power
required/preferred image brightness
field-of- view
primary purpose
usage conditions
comfort (very important)
COST/budget

Key Binocular Specifications

Primary specs, e.g. 7 x 35mm
7 = Power/magnification = the number of times an object is enlarged
35mm = diameter of the further lens in millimeters. Larger lenses capture more light and result in a brighter image.
Additional specs (optional)
B = eyepieces are suitable for people who wear glasses. The user can use these binoculars while wearing your glasses without losing much field-of-view.
GA = binoculars are rubber covered to protect against wear and tear
BA= binoculars are rubber-covered and have fold-down eyepiece cups.
WA = Wide-Angle design of the binocular’s eyepieces - able to increase a binocular’s of view by as much as 60%.
most often given as field with at a certain distance, e.g. 140m at 1000m (the actual width of the view 1000m away is 140m across)
sometimes expressed in degrees, but in general 1 degree is approximately equal to 17m at 1000m. So if WA=10degrees, then the view at 1000m would be 170m across.

More about power, brightness and field of view

Magnification, or power, is perhaps the most misunderstood and overly ‘hyped’ binocular feature. Higher powers can be useful, but almost always results in duller images and a binocular that is quite difficult to get a steady image with if handheld.
Also, the lower the magnification:

the wider the field-of-view
the brighter the image
the easier to use without a support (e.g. tripod)
the closer you can focus.

While powers of 7x to 12x are the most popular among regular binocular users, we recommend choosing the lowest magnification that would suit your needs, as it will make your entire experience much more satisfying. There is nothing as bad as needing a tripod when you don’t have one (due to your binocular’s limitation and not due to viewing conditions).

Lens diameter also an important consideration, since it is the primary determinant in the size/bulkiness of the binoculars. Again, find that happy medium - don’t go overboard with lens diameter and you’ll be much happier with your purchase. The field of view decreases as magnification increases, so select a binocular with lower magnification or a binocular classified as wide-angle if field of view is important to you .

The Prisms

The size, design and quality of the prisms used in the binocular design affect what you see and how clearly an image appears across your viewing area. You may prefer one binocular over another because of the design.

Porro Prism

These are the “traditional” binocular design with offset prisms and are the most cost-effective. They are however bulkier and less durable than roof prism models.

Reversed Porro Prism

This design allows for a compact binocular that easily fits in your hand.

Roof prism

These have parallel barrel, are more streamlined and very durable, but good optical quality in this design is quite expensive.

Size

Binoculars can be classified as either full-size or compact and is affected by the size of the objective lens. Full-size models offer the greatest light gathering ability and over-all optical performance. Compact models are more portable than full-size models and work well during daylight hours, but not during twilight or in deep shadows.

Cost

We recommend that you buy the best quality binoculars you can afford since poor quality binoculars can be a great source of frustration. They also lead to eyestrain and headaches, which will force you to get get a better quality binoculars at much greater cost than if you chose quality right from the start. Again, power can be a price-booster - buy the least magnification for your purpose - the image quality will be much better in any case. Also remember that you can get better quality for your money by buying a used model that was well cared for. Amazon.com for example often offer new and used options, and you get the benefit of them ‘enforcing’ customer satisfaction criteria.

Waterproofing

Since binoculars are used in often unpredictable weather conditions, we recommend buying a waterproof model if you can afford it. They cost a bit more as they are actually submersible, but you’ll be able to use these binoculars without fear of getting them wet.