Skip to main content

Deciphering Binoculars

Deciphering Binoculars

Learn to distinguish the high-quality glasses from the kitsch.

There are a boatload of binoculars on the market these days, and making sense of the myriad claims, hype and gobbledygook terminology that fills the manufacturers' literature can be a bear. However, understanding just a few key terms and concepts and what's behind some of the buzzwords will help you find the best glass for your money.






Take the time to learn binocular terminology; it can mean the difference between a wise purchase and a wasted one.


A conventional binocular description--10x42, let's say--includes the magnification and the objective lens diameter in millimeters. Most optics makers say magnification is not as important as clarity, resolution and lens quality, because magnification is irrelevant if the optics are so dim that you can't see through them. True enough, but the whole point of having binoculars is to make far away things look closer, and the more magnification, the closer objects appear.


So first choose a magnification that meets your needs, then shop for the best optical quality you can afford. The higher the magnification, the better quality optical glass you'll need because all optical systems get dimmer as magnification increases. The only way to offset this is with high-grade lenses and prisms that allow superior light transmission.

On the objective lens side, bigger is better. The larger opening not only lets in more light and brightens your image but it also supports higher magnifications. Twenty years ago 7x40 was about as high as you could go. Today, technical advances in lens quality make 10x40 binoculars indispensable field tools. And premium optics makers such as Leica, Zeiss, and Swarovski are even offering crystal-view 10x32 glasses.

Given equal magnification and objective lens size, the sharpness, brightness and resolution of the image you see through two different binoculars depends on the optical quality of the glass. In a nutshell: The higher the grade of glass, the more expensive it is.

Binocular housings contain two glass objects inside: lenses and prisms. Lenses are round, flat pieces of glass stacked at the eyepiece and the objective end. Prisms are funny-shaped glass chunks that bounce light around to give you usable magnification, focal length and a right-side-up image.

Beyond these preliminary definitions things get pretty technical pretty quick, and--unfortunately--some of it you need to know.

Consider prisms. There are two basic types: Porro prisms, which are offset and route light at 90-degree angles; and roof prisms, which are overlapped and route light at more acute angles and are lightweight and compact. Porro-prism binoculars have the classic "stepped" offset look; roof-prism binoculars are slim and sleek with a straight-tube.

There are two types of roof prisms: Pechan (smaller) and Abbe-Koenig (larger). Pechan prisms have a mirror-type surface that inherently loses 4 to 6 percent of available light, so they are used in ultra-compact designs not intended for low-light conditions. Larger Abbe-Koenig roof prisms are employed in mid- and full-size instruments where twilight viewing is a factor.

Roof prisms are also more sensitive to "stray light" (light bouncing off the binocular's interior surfaces), and they require coatings to deliver premium resolution and contrast. In catalogs these are called: Phase-Coat, P-Coat, PC-3 Coat or something similar.

The higher the magnification, the better. But for serious hunting you also want binoculars with high-quality glass that has been fully multicoated.


Stray light is a real problem in binocular design, and top-end makers have developed a separate technology of interior-surface finishes, surface-angle reductions and component holders to reduce it to an absolute minimum.

Also, because roof prisms route light at sharper angles, they require higher-grade glass to equal Porro prism performance. There are nearly as many different "alloys" of glass as there are alloys of aluminum or steel. Premium roof prisms typically employ barium crown glass (Bak4 is the most common grade). Porro prisms (and less-premium roof prisms) commonly employ cheaper Bk7 borosilicate glass.

Roof prism binoculars generally cost more than Porro prism binoculars of equal magnification and optical performance. But at any given magnification/objective level, Porro prisms provide slightly better depth perception and wider fields of view than roof prisms. However, roof prism binoculars are much more popular these days because they are so much sleeker, more compact and, well, cool-looking.

Similar quality issues apply to lenses as well. When light passes through any piece of glass, the light is dispersed into component colors, and delivering a sharp, clear image to your eye requires a system of lenses in the objective and eyepiece ends of the binocular that correct any color fringing (technically, "chromatic aberration"). The result is a chromatically corrected or "achromatic" system, but even achromatic systems will display small residual aberrations that can become distracting and eye-fatiguing at magnifications of 10X and above or in extreme light situations (either very dim or very bright).

The solution is to use a notably more expensive and somewhat heavier extra-low dispersion or anomalous partial dispersion glass. Depending on brand, this glass may be called ED, fluoride, HD, EDX or APO glass, and such systems are termed "apochromatically color corrected" or "superachromatic." These are important keywords to focus on when shopping.

Lens coatings are another important consideration, and have a great effect on light transmission and image sharpness. Purchase the most complete coating level you can afford. Commit these terms to memory: coated (single coat on at least one lens surface); fully coated (single coat on all glass-to-outside air surfaces); multicoated (multiple complementary-function coats on at least one lens surface); and fully multicoated (multiple coats on all glass-to-air surfaces)

Avoid mere coated binoculars; they're not worth the money. Fully coated lens systems are minimally okay for daytime use.

You'll find multicoated lenses in a wide range of quality midlevel products, and all premium binoculars have fully multicoated lenses these days.

Remember, I'm just talking about lens coatings; the phase-coating on interna

l prisms is something else entirely and will be specified separately in a manufacturer's product descriptions. Premium binoculars are fully multicoated and phase-coated.

When researching binoculars, keep in mind that if manufacturers don't specifically mention high-grade features, then they aren't there. If all their lenses are "fully multicoated," they'll tell you.

You'll spend much more time looking through your binoculars than through any riflescope, which to my mind means that the optical quality of the binoculars is actually more important.

Looking at poorly resolved and distorted images causes eye strain, and eye fatigue hurts. I've had many, many hunters tell me that they don't like to use binoculars because they can't seem to see through them comfortably. That's because they've got crappy binoculars.

GET THE NEWSLETTER Join the List and Never Miss a Thing.

Recommended Articles

See More Recommendations

Popular Videos

Mossberg Patriot Predator 6.5 PRC Rifle Review

Mossberg Patriot Predator 6.5 PRC Rifle Review

RifleShooter Magazine editor Scott Rupp breaks down all the features of the Mossberg Patriot Predator rifle chambered in 6.5 PRC.

Marlin Model 1895 in .444 Marlin

Marlin Model 1895 in .444 Marlin

Introduced in 1965 with the .444 Marlin cartridge, the Model 444 was the most powerful lever action of its day.

New for 2021: Caldwell AR500 Steel Range Targets

New for 2021: Caldwell AR500 Steel Range Targets

The Caldwell AR500 steel targets are offered in seven sizes and various hanging solutions to fit your specific shooting range needs.

New for 2021: Crimson Trace Brushline & Hardline Scopes

New for 2021: Crimson Trace Brushline & Hardline Scopes

New riflescope models from Crimson Trace are the Hardline, for the tactical-shooter, and the Brushline, for the hunter.

See More Popular Videos

Trending Articles

The Christensen Arms lightweight Mesa Titanium Edition bolt-action hunting rifle is a peak performer.Christensen Arms Mesa Titanium Edition Rifle Review Reviews

Christensen Arms Mesa Titanium Edition Rifle Review

Brad Fitzpatrick - August 14, 2020

The Christensen Arms lightweight Mesa Titanium Edition bolt-action hunting rifle is a peak...

A simple test of sorting ammo and a shooting session at the range will show how bullet runout can affect the accuracy of your rifles.Bullet Runout - How It Affects Accuracy Shooting Tips

Bullet Runout - How It Affects Accuracy

Joseph von Benedikt - May 13, 2019

A simple test of sorting ammo and a shooting session at the range will show how bullet runout...

Ruger's newest Hawkeye, the Hunter, blends classic and modern features to create an accurate, all-purpose hunting rifle.Ruger Hawkeye Hunter Rifle Review Reviews

Ruger Hawkeye Hunter Rifle Review

Brad Fitzpatrick - November 20, 2020

Ruger's newest Hawkeye, the Hunter, blends classic and modern features to create an accurate,...

You're only as good as your weakest link; heed these to tips to make sure your shooting skills don't hinder your rifle's accuracy potentialHow to Shoot Your Best from a Benchrest Shooting Tips

How to Shoot Your Best from a Benchrest

Keith Wood - August 05, 2014

You're only as good as your weakest link; heed these to tips to make sure your shooting skills...

See More Trending Articles

More How-To

 Hornady's Lock-N-Load OAL tool (straight and cuved, red) and Sinclair's seating depth tool (black)Getting The Right Overall Length How-To

Getting The Right Overall Length

Joseph von Benedikt - December 11, 2017

Hornady's Lock-N-Load OAL tool (straight and cuved, red) and Sinclair's seating depth tool...

A look at riflescope mounting setups, past and present.Rifle Scope Mounting Set-Ups How-To

Rifle Scope Mounting Set-Ups

Layne Simpson - December 20, 2019

A look at riflescope mounting setups, past and present.

During those months without an open season, use that time to do some prep work with this to-do listTo-Do List for the Rifleman During the Offseason How-To

To-Do List for the Rifleman During the Offseason

Craig Boddington - March 10, 2015

During those months without an open season, use that time to do some prep work with this to-do...

It's such a wonderful experience; picking out a new rifle can be as exciting as Christmas morning to an eight-year-old.The Art of Choosing a New Rifle How-To

The Art of Choosing a New Rifle

RifleShooter Online Staff - August 20, 2018

It's such a wonderful experience; picking out a new rifle can be as exciting as Christmas...

See More How-To

Magazine Cover

GET THE MAGAZINE Subscribe & Save

Digital Now Included!

SUBSCRIBE NOW

Give a Gift   |   Subscriber Services

PREVIEW THIS MONTH'S ISSUE Arrow

Buy Digital Single Issues

Don't miss an issue.
Buy single digital issue for your phone or tablet.

Buy Single Digital Issue on the RifleShooter App

Other Magazines

Special Interest Magazines

See All Special Interest Magazines

GET THE NEWSLETTER Join the List and Never Miss a Thing.

Phone Icon

Get Digital Access.

All RifleShooter subscribers now have digital access to their magazine content. This means you have the option to read your magazine on most popular phones and tablets.

To get started, click the link below to visit mymagnow.com and learn how to access your digital magazine.

Get Digital Access

Not a Subscriber?
Subscribe Now