Field of View

The Field of View (FOV) is the area that can be seen when you are looking through the binoculars. Binocular specifications will generally refer to three measurements in regard to the Field of View:

·        Angular Field of View (Real)

·        Angular Field of View (Apparent)

·        Field of View at 1000mtrs

The Angular field of view is measured in degrees. You can roughly calculate the linear field of view (field of view at 1000mtrs) by multiplying the angular field of view (real) by 17.5. Take for example Canon 12x36 IS II Binoculars. The real field of view is 5^o so if you multiply 5 x 17.5 you come up with the linear field of view which is 87.5mtrs.

The Angular field of view (apparent) is the real field of view multiplied by the binoculars magnification power so continuing to use the Canon 12x36 IS II Binoculars as our example, they have a real field of view is 5^o  and a magnification power of 12, 12 x 5 = 60 ^o .   

As you can see the field of view is related to the magnification powers of the binoculars, the higher the level of magnification the smaller the field of view (as a general concept). If you are viewing fast moving objects it’s desirable to have a wide field of view which makes is easy to find the object that you want to view such as planes or birds.

Image Stabilizing

Image stabilizing (IS) binoculars include an image stabilizing facility which enables them to be used in moving environments (including cars or boats) without the image being distorted. I addition they enable high magnification binoculars to be used as hand held binoculars without the image being distorted due to movements in the hand. One of the main downsides of image stabilisation is that the weight of the binoculars. One of the most popular choices with image stabilising technology is the Canon 10x42 WP IS binoculars.

Individual Focus

Individual focus means that each eyepiece has to be separately focused which generally makes focusing slower. Central focusing is more common.

Lens Coatings

The binoculars optical coatings play an important role in the quality of image. Coated lenses ensure an even light transmission through the binoculars which results in a clear, sharper image.

There are 4 basic types of coating with the most basic binoculars having no coating at all. With uncoated lenses less than half the light is transmitted through the binoculars which will significantly impact on the quality of the image, delivering an excessive amount of glare and low image contrast. Binoculars with uncoated lenses are not recommended.  

·        Coated means that one or more of the lenses are coated, with a single coat, which offers little improvement over uncoated lenses. The overall image quality with binoculars that are just ‘coated’ is poor.

·        Fully Coated means that all glass surfaces (that are exposed to air) are coated with a single anti-reflection layer. The image quality provide by such binoculars is acceptable for most users.

·        Multi-coated means that one or more surfaces are coated with multiple layers of anti-reflection coating and the other surfaces are coated with a single coating. Multilayer coatings increase light transmission and improve image quality which will result in brighter, sharper images.

·        The best quality binoculars are fully multi-coated which means all surfaces exposed to air have multiple anti-reflection coatings. Fully multi-coated lenses maximise the amount of light that is transmitted through the binoculars resulting in the greatest image clarity.

 

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