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10 Myths
about
Birding Optics

from Bird Watcher's Digest, August, 2006
Michael Porter Diane Porter
by Michael and Diane Porter

Every subject has its myths, misconception, and urban legends. They spread and persist like gossip, but are even more unreliable. Birding optics is no exception. Maybe we can?ft set the record straight about what the neighbors are saying about your love life, but perhaps we can shed a little light on the subject of binoculars and scopes.

Here are 10 common myths about birding optics.

MYTH #1?| Higher power binoculars will let you see more.

REALITY ?| Actually, with a higher power binocular you may end up seeing less!

One would think that the more magnification, the more you could see. But it?fs not necessarily so. The usable power of a binocular is limited by the steadiness of the hands that hold it. And even a birder with normally steady hands won?ft be able to hold a binocular as still after running up a steep hill to see a bird as the same person sitting quietly on the back porch. There is an inevitable wobble in any handheld binocular?fs image. The higher the magnification, the greater the wobble. At some point, the wobble negates the increased resolution that magnification provides.

It?fs generally agreed that 10 power is the upper limit of hand-holdable binoculars. That?fs why few binoculars with over ten power are marketed to birders.

Many experts believe that birders can see just as much or even more with 8 power binocular, or even 7 power. This is particularly true when a birder?fs muscles are fatigued. While watching warblers in the treetops, for example, the longer a birder?fs arms are raised, the harder it gets to hold the binocular steady.

To get a sense of how much the shaking of your hands degrades a binocular image, try stabilizing your binocular on a tripod. You may be surprised how much more detail you can resolve than you can when holding the binocular in your hands.

The bottom line is that a binocular with higher magnification might not let you identify more birds. What you need may not be ?gstronger?h binoculars, but better ones.

MYTH #2 ?| Bigger binoculars are more powerful.

REALITY ?| The size of the binocular tells you absolutely nothing about the power. Some10-power binoculars are smaller than some 7-power ones. For example, a Zeiss 10x25 Victory Compact is only three quarters as long and weighs one third as much as a Zeiss Victory FL 7x42.

What determines a binocular?fs power, or magnification, is the design of its eyepiece. And eyepiece design has little or no effect on the size of the binocular. Often a manufacturer makes the same binocular in more than one power.

For one example among many, the Pentax DCF HRII (pictured below) comes in 8x42 or 10x42. See if you can tell which one is the ten power.

Pentax size comparison

The look the same, don't they? By the way, you wouldn?ft be able to tell by their appearance even in you were holding them in your hands—not without reading the numbers printed on the outside. The two models have the same dimensions, shape, and weight, and the share the same sized objective lenses. The difference is in their eyepieces, one of which magnifies the image 8-fold and the other 10-fold.

Well, then, what does make a binocular bigger?

Mainly it?fs the size of the objective lenses. (The objective lenses are in the end of the binocular closer to the object you?fre looking at). In the formula printed on the binocular, the size of the objectives is the second number. Binoculars that are 7x42, 8x42, and 10x42 all have objective lenses that are 42mm in diameter. Binoculars in the same product line with the same sized objectives will usually be the same size.

Continued
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