Understanding Binocular Magnification

Find out how to crunch those numbers for a perfect viewing experience with these Pro Tips on binocular magnification.

August 21, 2019

Whether panning over your hunting ground or capturing a glimpse of a passing bird, binoculars can be great optical tools. But which binocular configuration is necessary to achieve that perfect picture? Vortex Optics’ Chief Media Ambassador Jimmy Hamilton has a quick overview to help you better understand binocular magnification. Use these optics Pro Tips during your next outing and get your sight right.




To begin, binoculars are identified by their power and objective lens diameter. The power is first in the description. For example, an 8x42 binocular carries a magnification of 8 power. “So, any image I see through these is going to be magnified eight times,” Hamilton says.


The objective lens diameter is the second number in the equation. While binoculars have two objective lenses, each is the described diameter. So, a binocular with “42” listed for its objective lens will have two lenses 42 millimeters in diameter. A larger objective lens can allow more light to pass through and create brighter, sharper viewing conditions. However, larger lenses can add weight to the binoculars themselves. This can compromise how easily they’re packed, held or used.


BONUS PRO TIP: You can determine your binocular’s exit pupil size with a quick equation. Divide the objective lens diameter by the magnification power. So, an 8x42 binocular will have an exit pupil of 5.25 millimeters.




You’ve now cracked the equation, but what is the right combination for your needs? To determine your best binocular strength and objective lens diameter, look at your primary location. Try to envision the landscape of your favorite hunting spot.


“You’re going to want to choose a lower magnification range, like 8- or 10-power binoculars, when you’re in an area of the country that’s really heavily wooded or dense foliage and you’re not going to be able to glass that far to find an animal,” Hamilton says. “When you’re in a more vast, open landscape, for example, that’s where you may want to start looking at a binocular with a higher magnification, like 10, 12 or maybe even 15 or 18.”




Not every magnification power can suit every outdoorsman. A higher magnification can also magnify your movements, which can affect your vision, according to Hamilton. For example, if you’re glassing without bracing your binoculars, you can risk moving too much for a clear picture. “A lower magnification will help you see whatever you’re looking at much better because it’s not going to magnify all those natural shakes that we have in our hands and our arms,” Hamilton says.


In addition, if viewing closer objects, a higher binocular power can zoom in too much. Too much magnification can fill your lens and make it difficult to make out your object. In these situations, it could be best to opt for a set with a lower power.


Opening your eyes to binocular magnification can help you achieve the best views possible. Use these Pro Tips to zero in on the perfect power and objective lens combination for you.