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post #5 of Old 06-23-2013
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Re: Binocular Conundrum: Field of View?

Originally Posted by hellosailor View Post
OK, I'm familiar with optics in general and the issues of binoc quality and choices to be made. But there's one variable that really is a conundrum to me, since no one bothers to explain it but everyone swears they aren't just making up numbers.

Field of View.

Take two sets of binocs, 7x50 or 10x42 or whatever you choose. Same size objective lens, same magnification, and same size exit pupil as well. Now look at the FOV and you may find one is rated for a 50% wider FOV than the other, despite the fact that the exit pupil and the objective lens size are the same, so in theory the "cone" of light has to be the same angle, and with the same magnification...I don't see how it is possible for the specs to be the same, the laws of physics to be the same, and yet somehow one pair of binocs is "seeing" a 50% wider angle on the FOV.

What's the hocus-pocus here? What aren't they saying that allows two "identical" optical systems to have such widely different cones of vision?
The field of view of the instrument is determined by the optical distance between the objective (front) and eyepiece lenses and has nothing to do with magnification. The farther apart the lenses are, the more narrow the field of view (think of the angle in a short fat cone verses a tall narrow cone). Generally a somewhat wider field of view is desirable for enabling one to pick up targets with somewhat less sweep or traverse of the field of view. I find that the field of view of the Fuginon Polaris binoculars is just about right.


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Last edited by svHyLyte; 06-25-2013 at 08:07 AM. Reason: correct typo's
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