JM Optics Ltd
Binocular and Scope Specialists
Field of View
The Field of View (FOV) of a binocluar is the size of the image that you can see. The larger the field of view, the more you can see more of the subject.
The are several factors that affect the field of view of a binocular, the most significant of which is a binoculars magnification. In general, a low magnification binocular has a wide field of view. As the magnification increases then the field of view decreases. Another significant factor is the quality of the lenses and prisms inside the binocular. As the quality of the lenses/prisms inside increase then the field of view will usually increase. The way the mechanism is designed will also affect the field of view. This means that at the same magnification, different models will probably have different fields of view.
A good field of view for an 8x magnification binocular is around 8°, while a good field of view for a 12x magnification binocular is considered to be around 4°.
One thing that does not have any significant affect on the field of view is the size of the front lens, so a 21mm front lens can have the same field of view as a 40mm front lens
Field of View Demonstration
Without binoculars the ship in the distance is very small.
At 8x magnification, the boat is much closer. These binoculars have a wide field of view because you can see most of the ship.
This image is exactly the same magnification as the previous one, but because the field of view is small you can only see a small part of the ship.
Spectacle Wearers
Most modern binoculars can be used while wearing glasses. (They can still be used without glasses as well.) If the binocular has soft rubber eyecups then these can usually be folded down so that the lens in the eyepiece (ocular lens) is nearer the lens of your glasses. Having both lenses close together in this way reduces 'tunnel vision' (and so increases the field of view) that can sometimes happen using binoculars while wearing glasses.
Some binoculars are designed with 'long eye relief'; this is especially for people who want to wear spectacles and use binoculars at the same time. Normal binoculars are designed to focus the image on the lens of the eye. Binoculars with long eye relief focus the image around 15mm (half an inch) in front of the eye. This does not stop them working for people who do not wear spectacles, but it means that the image is focused onto the lens of the spectacles. It then leaves the spectacles to fine tune the focus for the eye.
As you are viewing the products on the website lookout for the following image 
.It indicates that the binoculars have 'long eye relief'.
