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Old 07-02-2013
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Re: Binocular Conundrum: Field of View?

From a birding forum - in answer to the question "What determines field of view?"

"The short answer is the field stop in the eyepieces. The field stop is roughly the narrowest diameter of eyepiece, the widest piece of unobstructed glass. If you compare a narrow field binocular with a wide field binocular, other things being equal, the latter has the wider field stop.
To get a wide field with a sharp image across the greater part of the field requires a sophisticated design of the eyepiece."

Make sure you are comparing the same measures of FoV - there is real FoV; and there is apparent FoV which adjusts for magnification; and then there is the FoV at 1000 meters. FoV and apparent FoV are angular measurements and FoV at 1000 meters is a distance. The first two are the angles of the cone of light into the instrument and the last is the diameter of the base of the cone at 1000 meters.
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