Choosing Binoculars For The First Time
- Choose binoculars with a magnification of up to 12x.
Remember that just because binoculars have a magnification of over 12x is not a sure guide that the images will be better. If the binoculars will be for handheld use outdoors, then magnifications of between 6x to 10x are the best. Hand movements in binoculars with magnifications of 12x or higher will cause a person to see shaky images and negatively affect the viewing experience. Usually, a higher the magnification will reduce the real field of view.
- If a person plans on view broad areas, then binoculars with a wide field of view are best.
Having a wider the field of view makes it easier it is to locate objects. If the magnifications are exactly the same, the larger the value of real field of view, the wider the field of view.
- If a person wears glasses then it’s recommended to purchase binoculars with 15mm or longer eye relief.
For those who don’t wear glasses, then choose an eye relieve of around 10mm.
- Binoculars with a waterproof casing.
Having a waterproof casing on binoculars is always recommended. Then if there’s a sudden downpour of rain, or a spray of water, a person doesn’t have to worry.
Choose The Binocular By Specifications
For general users, it is recommended to use binoculars with a magnification of up to 12x.
- Higher magnification does not always mean better binoculars. How binoculars will be used, and in what situations, should then be taken into account.
- A higher magnification can cause a narrower field of view, and this can disadvantage in some instances. There are also problems that hand movements cause unstable images and the small exit pupil results in darker images.
- Therefore, if a person is planning to view moving objects or try and locate objects at large distance, high magnification binoculars should be avoided.
Are zoom binoculars better?
- Zoom binoculars have the advantage of providing a wide range of magnifications. For example, when using them in a concert hall, it is possible to zoom out to take in the whole atmosphere of the hall, then a person can increase the magnification get a close up of the stage performer or view specific scenes at higher magnification.
- Please remember that a higher magnification will result in a narrower field of view, unstable images due to hand movements. Therefore zoom binoculars may not be the best option for everyone.
Extremely High Magnifications
When using binoculars that have a very high zoom ratio such as 50x or 100x, then observation is much more difficult. Example: with 100×50 binoculars (100x magnification, 50mm effective diameter of the objective lens)
- A very narrow field of view makes it more difficult to observe objects.
- Images will appear darker because the exit pupil can be as small as 0.5mm. The smallest diameter that a human eye pupil will be in bright conditions is no smaller then 2mm. Therefore an exit pupil of 0.5mm will make the images too dark.
- Hand movements will adversely affect the viewed images. Therefore, these types of binoculars aren’t suitable to hand-held observation.
Effective diameter of the objective lens
The size of the objective diameter is directly related to the amount of light that can pass through the lens. Therefore magnification is the same. The result of this is that the resolution is higher and the image brighter. It must be noted though that because of the larger lens diameter, these kinds of binoculars are larger and heavier.
Exit pupil and brightness
The bright circle in middle of the eyepiece is the exit pupil. This can be seen when the binoculars are held pointed to a bright light and 30cm away from your eyes. A larger exit pupil diameter will result in a brighter image. This is an important fact if binoculars will be used in low-light conditions, for example at dawn, dusk or observing the night sky. To calculate the diameter of the exit pupil, you can use a formula which is :
Exit pupil = Effective diameter of the objective lens ÷ Magnification.
Real field of view
This is the angle of the field of vision which can be seen without moving the binoculars. It is measured from the center of the objective lens. A larger the value indicates a wider the field of view. Binoculars with a wide view field are ideal for locating and observing fast-moving wild birds and animals. This also is true for astronomical observations, where it is much easier to find clusters of stars or small nebulas.
Apparent field of view
The angle of the magnified field when looking through binoculars is the apparent field of view. This means that at high magnifications binoculars show a wide field of view.
For example, an apparent field of view of 8×7.0° binoculars is as follows:
2ω’= 2 x tan-1 (Γ x tan ω) = 2 x tan-1 (8 x tan 3.5°) = 52.1°
Field of view at 1,000m. At a distance of 1,000, and without moving the binoculars, this is the width of the visible area at a distance of 1,000 meters.
The distance measured from the outer surface of the eyepiece lens to the position where the exit pupil is formed (eyepoint) is the Eye relief. If a person looks through binoculars from the eyepoint then the whole field of vision can be obtained without the edges appearing darker (vignetting). For those who wear glasses, it is recommended to use binoculars which have a longer eye relief (high eyepoint) of 15mm or longer. Then objects can be viewed without the glasses being removed and with no vignetting.
Close focusing distance
This specifies the distance that to the nearest point that can be focused. Binoculars are designed used to make objects in the distance appear nearer. However, they can also be used to magnify images from a close distance.
This is useful if a person is studying plants and insects or wants to appreciate fine works of art. In this case, more details can be seen the shorter the focus distance of binoculars. About 1 to 2 meters is the minimum for close focusing.
In order to prevent fog and mold developing inside binoculars are often waterproofed. To achieve this, Nikon’s waterproofed binoculars are designed to keep body tubes airtight, and these are filled with nitrogen gas.
Although binoculars are waterproofed, they should not be used underwater. If waterproof binoculars do get wet, a dry cloth should be used to thoroughly dry them.
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