What do the numbers on binoculars mean?

Ever wonder what the numbers on a set of binoculars mean? You see pairs stamped with 8×25, 10×42, 12×50, etc. It’s important to understand those numbers when you’re picking out a pair of binoculars for target archery, hunting, watching sports, etc.

Take a walk through the field of competitors at a 3-D tournament and you’ll see basically every archer carrying a set of binoculars. They’re critical for 3-D archery because the scoring rings on the animal targets are not easily seen from the shooting line with the naked eye. If you want to find the black 12-ring on a black javelina target from 30 yards away, you’ve got to have the right binoculars.

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So let’s say you are looking through a set of binoculars that have “10×56” stamped on them. The “10” refers to the magnification. That is, those binoculars magnify images 10 times greater than what your naked eye sees. Another way of thinking about that is to say the binoculars make objects appear 10 times closer to your eye.

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If you’re using 10-power binoculars to look at a target that’s 40 yards away, the optics will make it seem as if the target is 4 yards away – 40 divided by 10. Obviously, you can see a lot more detail on a target that’s 4 yards away, as compared to 40.

Common magnification powers for binoculars are 6, 7, 8, 10, 12, 15 and 20 – with 8, 10 and 12 arguably being the most popular.

The second number on our “10×56” binoculars refers to the diameter in millimeters of the objective lenses. The objective lenses are those on the back side of the binoculars, which are farthest from your eyes. The term “objective” comes from the fact that these lenses are closest to the object being viewed through the binoculars.

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So our 10×56 binoculars have objective lenses that are 56mm in diameter. The bigger the objective lenses, the more light they will transmit to your eye, making them better for viewing in low light situations. However, the bigger the objective lenses are, the heavier your binoculars will be due to the increased size of the housing.

Also, assuming the magnification stays the same, the bigger the objective lenses are, the wider your field of view will be. That is, you will see more area around your target through a pair of 10×50 binoculars at a given distance than you will with a pair of 10×42 binoculars.

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Binculars with 50mm objective lenses at left; 42mm at right.

So what’s best for 3-D archery? A pair of binoculars that allows you to clearly see what you want to see on the targets at all shooting distances, which allow enough light to reach you eye, which you can comfortably carry with you all day long.

Those variables are going to differ from archer to archer.

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The 8×42 binoculars at left weigh 20 ounces, as opposed to the 28-ounce weight of the 15×50 bioculars at right.

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