Binocular Myths: Debunking the Legends

When you are shopping around for an important purchase, it's frustrating to find that the people who have the goods don't know much about them. It's even worse to discover that, although you've been given lots of information, it is misleading, confusing, or perhaps even dead wrong.

The binocular business is no exception. There are lots of reputable and knowledgeable dealers around. But there are also dealers who know nothing about binoculars, or worse, are ill-informed and only too happy to share their "knowledge."

Once a bit of misinformation finds its way into the binocular lexicon, it is often there to stay, and it can be very difficult to separate the facts from the myths. Here are seven commonly held myths and misconceptions and some suggestions to help keep your confusion quotient to a minimum.

1. Larger objective lenses offer a wider field of view.

Large objectives have their advantages and it makes sense that they might increase field of view, but this is not the case. Field of view in binoculars is determined first by the magnification; the higher the power, the narrower the field of view. Second, the eyepiece, through which your eye views the image, may be engineered to give a wider field of view. It's a simple matter to check the manufacturer's stated field of view on a few models and you will see that a 7x35, for example, will normally have a considerably wider field of view than a 7x50. (If you are having trouble equating a field of view given in degrees with one given as a number of feet at 1,000 yards, there is a simple formula: One degree is about equal to 52.5 feet at 1,000 yards.) Eyeglass wearers will find the field of view quite different than what is stated, except in the case of long eye relief binoculars. The most positive test is to look through the binoculars and see what you can see from left to right.

2. Rubber armoring makes binoculars waterproof.

Many of today's binoculars feature a nice rubber coating. This will quite effectively prevent moisture from getting through it, but it does not waterproof the binoculars. Water can seep in where lenses are seated, and sometimes at body joints (or joints in the rubber armoring). The most vulnerable spot on a binocular is the ocular tube, which slides in and out as the binocular is focused. It is possible to put O-ring seals on these tubes, but it is a difficult system to waterproof effectively. Some binoculars are focused by moving the objective lenses, but the same principles apply. The most reliably waterproofed binoculars will have a focusing mechanism that is completely inside the binocular body. Truly waterproof binoculars are also filled with nitrogen, which has no latent water vapor to condense on internal optics or foster growth of mold or fungus.

3. Rubber eyecups make binoculars suitable for eyeglass wearers.

This is only half a myth. Rubber eyecups, which can be folded down to allow be...

The Big Deal About Pocket Optics

• SIZE AND WEIGHT
• OPTICAL AND BUILD QUALITY
• CLOSE FOCUS AND FIELD OF VIEW
• EYE RELIEF
• WATERPROOFING
• EYECUPS
• STRAPS
• DANGLE FACTOR
• ERGONOMICS
• Putting it all together

The best binoculars in the world are useless if you don't have them with you. You know the story. You left them home because they were too heavy and you weren't intending to go birding anyway.

But birds can turn up anywhere, any time. A black-throated blue warbler might materialize in the mall's parking-lot shrubbery. Or a tufted duck could wander in from Europe and light on the river you drive across every day on the way to work.

But what if there were binoculars so small and light that you always had them with you? Something that would take up almost no room in your purse or pocket but still had excellent optics and rugged construction? You would always be ready and never miss a bird. Sound good? Then welcome to the world of pocket optics.

We collected 38 pocket binoculars from 17 manufacturers and assembled a team of southeast Iowa birders to try them out. We limited the entrants to those weighing less than 13 ounces. The lightest was only 5-1/4 ounces. All might fit into some sort of pocket, and a few can actually be carried in a shirt pocket. None of the binoculars we tested was over 4-1/2 inches long. They fell into two groups, roof prism design and reverse Porro prism design.

The smallest binoculars we tested were all roof prism design, in which the front lenses and the eyepieces are in a straight line. Roof prism binoculars are naturally compact. And furthermore, most of the pocket roofs can fold even smaller when not in use. The Porro prism group averaged somewhat larger. Although regular Porro prism binoculars have an obvious zigzag shape with the front lenses wider apart than the eyepieces, reverse Porros have the front lenses closer together than the eyepieces. This allows for a more compact package.

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Limitations of pocket binoculars

Are there tradeoffs for pocket convenience? Does everything look smaller? No, pocket binoculars can magnify the bird just as much as full-sized models. And the image can be just as sharp and clear.

However, there are some limitations. Their small objective lenses, usually only 20 to 25 millimeters in diameter, cannot deliver as bright an image in dim light as can binoculars with 42mm objectives. But in ordinary daylight, assuming they have good optics and lens coatings, pocket binoculars will seem just as bright as their larger cousins.

The field of view is often narrower, but not always. Field of view is actually related not to size, but to eyepiece design. For example the Pentax DCF binoculars offer a 330-foot field of view at 1,000 yards both with the standard-size 8x42 model and with the pocket 8x22 model.

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Size and Weight

Smaller is better as long ...

Getting Rid of the Pain in Your Neck

Are your binoculars a pain in the neck? I mean that literally. After an hour of birding is your neck sore? Is there a dull ache in your shoulders? Do you feel a dead weight hanging from your neck? These common complaints can all be traced directly to your binoculars.

Actually the cause of these problems is not your binoculars. The real culprit is the neck strap on your binoculars. Binoculars can weigh as much as two pounds. All this weight transfers directly to your neck through the narrow neck strap. This full weight continually bites into your neck, often for several hours. Every time you take a step, your binoculars bounce and the jolt digs into your neck. When you bend, they sway. If you duck under a branch, they swing, causing further strain to your neck muscles. Unfortunately, neck muscles are not designed for this kind of punishment. No wonder your neck gets sore!

The neck straps supplied with most new binoculars, even very expensive optics, are often inadequate for the purpose. The typical neck strap is a thin, hard plastic strip about one-half inch wide. It is too narrow and too inflexible. The full weight of your binoculars hangs by this skinny strap. Only a short section of the strap, maybe four or five inches, actually rests on the back of your neck. In technical terms, if your binoculars weigh two pounds and your strap is only one-half inch wide, your neck feels a constant pressure of one pound per square inch. That may not sound like much. But over a long period of time, the continual pressure takes its toll.

Fortunately there are ways to reduce or eliminate the strain and the resulting soreness in your neck. The solution is to remove the factory-equipped strap on your binoculars and throw it away. Replace it with a different, better strap. There are several commercially available straps specifically designed to ease neck pain.

A simple approach is to use a wider strap. Replace the half-inch wide strap with one that is one to two inches wide. A wider strap spreads the total weight over a larger area, thus reducing the concentrated stress on your neck. If you double the width of your strap, you cut the pressure in half. Tripling the strap width, reduces the pressure to one-third. Have you ever noticed the straps used by bird photographers toting heavy cameras with long lenses? Their straps are very wide, maybe up to three inches wide. The greater the width of the strap, the lower the pressure becomes in each square inch. Check out various camera straps at your local camera or optic store. Or scan the advertisements for mail-order camera and optics firms in magazines. They will carry wider straps.

You can also find commercial neck straps that go one step farther. These straps reduce not only the stress, but also the sudden jolts and jarring pains that shoot through your neck when your binoculars bounce as you stoop under a limb or hop from rock to rock. Standard nec...