How to buy binoculars?

Binoculars simply do 2 main things for you. They increase the size of the image you are viewing, and they let more light in than your eyes can - making images appear brighter in low light conditions. The ideal binocular doesn’t exist, the consumer needs to decide on weight and usage.  Before you make your purchase consider what you will be using the binocular for. Let's start off with some of the features commonly seen in binoculars and what they can be used for.

Binocular Performance

The Brightness and sharpness you see through a binocular is determined by a number of factors:

  • Magnification, also known as Power
  • Optical coating
  • Lens diameter
  • Prism Type / Grade
 

 

1) Maginification or Power

Magnification is the degree to which the object being viewed is enlarged. Binoculars are often referred to as number followed by an x i.e. 7x50. The first number indicates the power an object can be brought closer compared to a normal eye. The lower the magnification, the brighter the image, higher power will reduce the field of view.                                   

The ideal magnifications are:

  • In daylight observation 6x - 8x
  • From dusk to dawn   7x - 10x
  • For observation in mountains 10x - 12x
  • Hunting     8x - 12x
  • Water sports   7x
  • Astronomy   15x - 70x

 

2) Types of coating

The type and quality of coating will determine the following:

  • Up to 30% of light gathering can be lost if optics aren’t coated.
  • The quality of the coating increases the light gathering and results in a brighter image
  • In the centre of the image the sharpness is the highest
  • The lower the difference in sharpness of the image in the centre compared to the outer side, the higher the quality

 

3) Lens diameter

The second number in the formula (i.e. 7X50) indicates the front lens diameter in mm. The larger the objective lens the more light enters the binocular and the brighter the image.

  • On a 6 – 8 magnification 20-32 mm is normal
  • On a 7 – 9 magnification 35 – 50mm is normal
  • On a 10 – 36 magnification 50 – 70mm is normal

 Doubling the size of objective diameters quadruples the light gathering ability. But in reality the size of the lens must be considered along with the exit pupil and intended usage.

 

4) Field of view

This is the side to side measurement of the circular viewing field. It is defined by the width in meters of the area visible at 1000 meters. The higher the magnification, the narrower the field of view. A wide field of view is recommended to follow action ( i.e. sport)

Binoculars with a wide field of view usually have a magnification between 2 and 6. Some binoculars offer wide angle eyepieces which increase the field of view compared to the normal eyepieces.

 

5) Prism Types

The prism system of a binocular reduces the size needed to provide focal length. It turns the image that is upside down to the right side up. The most common quality standards of prisms are expressed as follows

  • BAK-4 prisms are made of barium crown glass (Higher Density)
  • BAK-7 prism are made of boro-silicate

 The difference is that the BAK 4 prisms have a higher glass density eliminating more light scattering and offering sharper images.

 

What do I use it for?

Bird Watching

For bird watching an 8x21 model may be fine on a bright day for observing a bird approximately 3 to 6 metres away. But, if you’re observing an eagle’s nest 800 metres away, a 15x70, 12x50, 20x50 model on a tripod may be sufficient. In practice you would expect to encounter different light conditions and expect to move from distant focusing to very close focusing. Under those conditions it is recommendable to take the following binoculars into consideration:

8X32 8X42 10X42 8X56 7X50

 

Sports 

For sports, if you are in a stadium, depending upon where your seats are located if you are between the middle and the first few rows you would prefer 8X21 8x32 7X35, whilst if you are sitting between the middle and the upper end you would prefer to have a 10X42 10X50.

Depending on the time of the event, late afternoon or early evening, you would need to take a binocular with a larger objective lens for better viewing.

 

 

Astronomy

For astronomy, a 7x50 model may be fine for observing the moon. To see more details on planets, you’ll need a larger and more powerful objective such as an 8x56, 9x63, 12x50, 15x70, or 25-45x100. Of course, a tripod will be needed for the larger binoculars due to the size, weight, and magnification.  Choose a binocular that has 5mm of Exit pupil or more for best viewing pleasure.

  

 

Backpacking and wildlife

For backpacking, you may want to keep your weight to a minimum and prefer to carry a pair of compact binoculars such as an 8x21, 8x25, 10x25 or 12x25 or even a monocular. However, if you are serious about observing distance scenery or wildlife, you may not mind the extra weight of 7x50, 8x40, 8X32, 8x42 in order to obtain more magnification and/or better resolution or light gathering ability.

  

Marine

For most boat owners or those observing close to the water the ideal binoculars will be a 7x50 waterproof. It offers good performance under low light conditions whilst at the same time it offers a very good field of view and a very good stabilization. For some people a 10X42 and 10X50 is a good alternative.  Keep in mind that the higher the power the lower the stabilisation capacity.

  

 

I think it's safe to say choosing the right binoculars for YOU is not an easy task. But we have product experts at hand to assist you with your choice, so don't forget to give us a call: 011 781 1323 or send us an email at sales@actiongear.co.za. You can always use our online chat service as well (bottom right corner)