Field of View of Binoculars
When looking through a binocular, the widest dimension of circular viewing area that you can see is described as the field of view. This is usually measured either in terms of linear feet at 1000 yards or in terms of angular degrees. Each degree of field corresponds to 52.5 feet at 1000 yards and binocular fields of view will generally range from 5 degrees (263 feet) to 11 degrees (578 feet). As a general rule, the field of view will decrease as the magnification increases so a 10 power binocular will usually have a smaller field of view than a 7 power. Field of view, however, is mainly determined by optical design of the ocular (eyepiece) and rarely a function of the size of the objective lens.
For observing at close quarters in deep woods, scanning the sky for raptors or large flocks of migratory birds or for picking up fast moving objects, a wide field of view is desirable. Wide-field binoculars, however, tend to be heavier and bulkier than binoculars with standard fields (because they employ larger prisms and eyepieces) and on many models there is a noticeable loss in sharpness at the edge of the field. Also, if you have too large a field (9 to 11 degrees, for instance) the object you want to observe may become lost amid the confusion of its surroundings. Another problem is that people who need to wear eyeglasses when viewing will usually have difficulty seeing the complete field with wide-angle optics. Wide field binoculars are generally the most popular for nature observation but you should consider all these factors in your evaluation of this feature.
Thanks to our friends at Eagle Optics for providing this information!
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