Monday, January 11, 2016

Does larger aperture mean wider field of view?

Hello EO,
I plan to purchase either the Eagle Optics Ranger ED 8x32 Binocular or Eagle Optics Ranger ED 8x42 Binocular.  I was surprised that the Field of View for the 8x42 (341’/1000 yds) was less than the 8x32 (393’/1000 yds).  Why is that?  

Shouldn’t the wider objective lens of the 8x42 (42mm) give a broader field of view than the 8x32 (32mm)?  

Is there an advantage of one over the other?

Thank you very much.
David J.

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 Dear David,
Thanks for your inquiry. It’s true that the shorter-barreled binoculars have a wider field of view (excluding compacts), though lots of people, like yourself, assume the opposite would be true. Field of view doesn’t increase with larger objective lens sizes. In fact, the Eagle Optics Ranger ED 10x50 Binocular has an even narrower field of view than the 42mm and 32mm Ranger ED.

You might find this video helpful for a more detailed explanation of aperture size, and  here is a brief article from our website to illustrate FOV.

The 32mm Ranger ED is the one to choose if you want a more lightweight binocular with wider FOV. However, it won’t be quite as bright in low light as the 42mm Ranger ED would.

Let me know if I may be of further assistance.

All the best,

Eagle Optics

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