Hunting Binoculars

What the two numbers on hunting binoculars mean

Every hunting binocular is named by two numbers. Take 8x42.

• 8x is magnification. One maker's binocular primer puts it simply: an 8x binocular makes a deer look as if you were standing 1/8 as far away.
• 42 is the objective, the front lens, in millimeters. A bigger front lens lets in more light and adds size and weight.

Those two numbers decide most of the others. Exit pupil, field of view and how steady the image looks all follow from them. The rest is build: prisms, sealing, eyecups and weight.

The table on this page lists binoculars their makers sell for hunting, sorted by magnification. It shows magnification and objective, field of view, eye relief, exit pupil, prism type, the maker's waterproof and fogproof wording, weight, and whether the binocular has a built-in rangefinder or image stabilization. The maker's numbers come first, with the Amazon listing's where the maker is silent (marked as listing values; weight is the maker's alone). A dash means neither states the value. We don't guess.

There are sibling pages for the two most common shapes, 10x42 binoculars and 12x50 binoculars, and one for rangefinder binoculars. This page is the whole category.

What to look at when you pick hunting binoculars

Here's what actually changes from one pair to the next, in the order I'd check it.

Pick magnification for the cover you hunt, not the farthest deer you've seen

Magnification is the trade you make first. More power shows more detail. It also shows more shake, a narrower slice of woods, and less light.

One binocular maker's hunting guide splits it by habitat:

• Dense cover (timber, stand hunting, hunting on foot): 6x to 9x
• Open country (mountains, sage flats, glassing from a truck or tripod): 10x to 18x

Another maker's whitetail guide lands on 8x42 or 10x42 for deer, from cornfields to deep woods. Its reasoning: enough power to glass, not so much that you need a tripod. Choose the 8x for a larger exit pupil and wider view. Choose the 10x if you need the reach.

The binocular primer adds the physics. Higher magnification makes the image more sensitive to hand shake and narrows the field of view. At 12x and up, you'll want a rest. (A tree trunk counts. So does Uncle Walt's shoulder, though he charges for it in complaints.)

Objective size buys light, and you carry the bill

The objective is the front lens. More millimeters, more light in, more glass to carry.

A 42 mm objective is the common middle. A 50 mm objective gathers more light for the same magnification, which is why 12x50 and 10x50 exist. Smaller objectives make compact binoculars that fit a jacket pocket, but they give up light. The table lists the objective right next to the magnification so you can see both halves of the name.

If you hike a long way in, weight may matter more than light. The hunting guide above makes the same point for backpack hunters: lighter glass, even at lower power.

Exit pupil is the dawn-and-dusk number

Exit pupil is the width of the beam of light that leaves each eyepiece, in millimeters. You can see it: hold the binocular at arm's length toward a bright sky and look at the small bright circle in the eyepiece.

Quick math, from an optics maker's knowledge base: divide the objective by the magnification.

• 8x42: 42 ÷ 8 = 5.25 mm
• 10x42: 42 ÷ 10 = 4.2 mm
• 10x50: 50 ÷ 10 = 5 mm

Why care? That same knowledge base says a dark-adapted eye opens to about 5 to 7 mm. An exit pupil that fills it delivers more light when it's dim. In daylight, your pupil shrinks and a large exit pupil buys you little. The hunting guide calls about 5 mm the useful target for low-light glassing.

Deer move most when the light is worst. So if you hunt first and last light, exit pupil matters more than almost any other number in the table.

Field of view decides how fast you find the deer

Field of view is how wide a slice of the world you see. US makers usually state it in feet at 1,000 yards, and the table uses that unit. Some state it in degrees instead.

The two convert. One maker lists a 10x42 at 309 ft at 1,000 yards and also as 5.9 degrees. Another lists a 10x42 at 334 ft and 6.2 degrees. So a degree is a little over 50 ft at 1,000 yards. Close enough to compare two pairs on paper.

Wider helps most in timber. A deer stepping through hemlocks at 60 yards is easier to pick up in a wide view than a narrow one. The hunting guide pairs dense cover with around 340 ft at 1,000 yards or wider, and open country with less. Lower magnification generally gives you the wider view.

Eye relief matters most if you wear glasses

Eye relief is how far your eye can sit behind the eyepiece and still see the whole field. The optics knowledge base recommends at least 10 mm and calls 15 mm the most comfortable. Glasses push your eye back, so eyeglass wearers may need more. The binocular primer suggests 14 mm or more.

The eyecups are the other half. One maker's binocular manual says to keep twist-up eyecups fully extended without glasses and twisted down with them. If you see a dark ring around the view, your eye is in the wrong spot. (It's the optical version of sitting too close to the TV, except the TV is strapped to your face.)

Roof or porro prisms changes the shape more than the season

Prisms flip the image right side up inside the binocular. There are two designs, and the table names which one each pair uses.

• Roof: straight tubes and a trimmer shape. A hunting magazine's optics column says roofs are popular because they're compact, and that they cost more to build because the design needs precision manufacturing.
• Porro: the offset, broad-shouldered shape. The same column calls porros slightly bulkier, and says that at the low end an inexpensive porro is generally better than an inexpensive roof.

An optics maker's knowledge base adds that roof prisms need special coatings to keep the image crisp, because of how the light path folds. Neither design is wrong for deer. If slim and light matter most to you, that's the roof column.

Waterproof and fogproof come from seals and gas

Binoculars fog inside when warm, moist air meets cold glass. Makers fix that by sealing the body and replacing the air inside with a dry gas. One maker describes its build as O-ring sealed and nitrogen purged for waterproof and fogproof performance.

The table repeats each maker's own wording, including gas type and any IPX rating where it's stated. If a maker doesn't claim it, the table doesn't either. Outside fog on cold lenses is a different problem; that one you wipe.

Weight is the number your neck reads

Weight is listed in ounces, from the maker, never from a store listing. For scale, one maker lists its 10x42 at 21 oz. Bigger objectives mean more glass and more ounces.

Weight matters most on long walks and in long sits with the binocular hanging from your neck. If it's heavy, a chest harness spreads it out. More on that on the binocular harness page.

Image stabilization and built-in rangefinders are extras with batteries

Two columns in the table are yes-or-no extras.

• Image stabilized: sensors and a moving prism or lens cancel hand shake. The binocular primer describes gyro-driven and flywheel designs. Both need power, and they're heavier. The column says yes only when the maker says so.
• Built-in rangefinder: a laser in the binocular gives you yardage. It has its own page, rangefinder binoculars, with its own specs.

If you hunt deer inside 40 yards from a stand, neither is required. They solve open-country and long-range problems.

Deer hunting binoculars by how you hunt

Walt has kept the camp logbook in pencil since 1991. Date, wind, temperature, stand, and a column for what moved. The early entries in that column are short. Some just say "deer?" with the question mark. Better glass is how the question mark goes away.

From a tree stand or saddle in timber

You're looking at short distances through branches, often in poor light. Start at 8x42. You get a wide view, a large exit pupil and an easier one-handed hold. Wear it on a harness so it isn't swinging when you climb. Stand gear lives in the blinds and stands section.

Over fields, food plots and power-line cuts

Longer looks, more daylight at the edges. A 10x42 gives you the reach and still hand-holds. If you sit at a field edge until last light, a 10x50 keeps the exit pupil at 5 mm.

Still hunting and spot-and-stalk

You're moving, so weight and quick handling count. A smaller, lighter 8x or a compact pair rides better. You'll raise and lower it a hundred times, so make it easy.

Out West or across big country

This is where 10x and 12x earn their keep, and the hunting guide says glassing from a tripod becomes normal. A 12x50 on a tripod adapter can pick apart a distant hillside a hand-held 8x can't. The 12x50 page covers that size.

Setting up hunting binoculars before the season

Do this at home, not at 5:45 a.m. in the stand. One maker's binocular manual gives the order.

1. Set the eyecups: fully up without glasses, down with them.
2. Set the width: rotate the barrels until you see one round image with no shading. That's your interpupillary distance (the space between your pupils).
3. Focus with the center wheel: pick an object about 20 yards away, close the eye on the diopter side, and turn the center focus until the object is sharp for your other eye.
4. Set the diopter: switch eyes (close the first one, or cover its objective lens with your hand) and turn the diopter until the object is sharp for this eye too.
5. Write the diopter setting down: the manual says to make a note of it in case you need to set it again. From then on, focus with the center wheel only.

I keep mine on a strip of tape inside the case lid. Walt keeps his in his head, which is why he refocuses every morning.

Care in the field

Lens coatings scratch easier than you'd think. The same manual's method:

• Blow or brush off dust and grit before wiping: canned air or a soft camel-hair brush
• Fog the lens with your breath, then wipe with a non-abrasive lens cloth
• Lens cleaning fluid and optical paper for anything stubborn
• No facial tissue, heavy cotton or flannel, which can scratch a lens

Use the rain guard and lens covers whenever you're not looking through the glass. After a wet day, the manual says to keep the caps off and let the binocular dry out completely before it goes back in the case.

Never look at the sun through binoculars. The manual warns it can damage the retina and cornea, even to the point of blindness.

Who can skip hunting binoculars for now

If you hunt a small food plot from one ground blind and every shot is inside 20 yards, your eyes and a rangefinder may cover it this season. Buy binoculars when you start asking "what moved" and can't answer it. Hunting rules vary by state, so check your state wildlife agency before you go.

When you do buy, write the diopter number down. Walt will tell you he doesn't need to. Walt also refocuses every morning.