Binoculars:
How 8x Is more than 10x

by Michael and Diane Porter

Why doesn't everyone always buy 10-power binoculars? They usually cost only a little bit more than 8-power binoculars.

At first thought, it seems as if 10 power would be better than 8x, but that's not necessarily true. Many expert birdwatchers insist that they see just as much detail, or even more, with an 8-power binocular as they do with a 10-power. Here are the ways that an 8-power binocular can give you more than a 10-power binocular.

1. More steadiness to the image

Everyone's hands shake — a little or a lot — but no living, breathing human being has perfectly steady hands. The binocular's magnification increases not only the size of the image, but also the apparent shakiness.

So the more you magnify, the more the image is jumping around. At some point, the advantage that comes from making the image larger just gets overwhelmed by the unsteadiness of the hand.

That is why many people find that they will actually see just as much detail with the lower 8-power magnification. In fact, some people actually prefer a 7-power binocular, such as the magnificent Zeiss Victory FL 7x42.

Another very popular binocular, with even lower magnification, is the excellent (and relatively inexpensive) Leupold Katmai 6x32.

2. Wider field of view

You usually get a wider field of view with an 8-power binocular than you do with the same model in 10 power. Interestingly enough, the smaller, lighter-weight 8x32 version often has the widest field of view of all.

A wider field of view makes it easier to spot a bird among the branches or a duck on the waves. In the photo below, the magification is greater on the right, with 10-power binoculars. (Just the tip of the cardinal's wing is visible, at at 2 o'clock.) But notice that more of the scene is in the left picture. All you have to do to find the bird is get it anywhere in the image. That's why it's easier to locate the bird with the lower-power binocular.

Seen through 8-power binocular	Seen through 10-power binocular

The table below compares the field of view (in feet, at 1000 yards) of some typical binoculars, in 8x and 10 powers.

3. More eye relief.

In most binocular models, the eye relief is greater on the 8x42 version than on the 10x42 version or the 8x32 version is there is one.

As the sampling below shows, this is not always the case. In the Leica Ultravid HD, the 10x42 has slightly longer eye relief than the 8x42.

Eye relief matters only to people who wear glasses. But if that's you, you'll want to pay special attention to the eye relief, especially when considering a 10-power binocular. For glasses wearers, 16 mm of eye relief is minimal, but it's better to get a binocular with 17 mm to 20 mm of eye relief. Zeiss doesn't really fit in this chart, because the Victory FL's eye relief is good even though it's listed as 16mm. (See sidebar at right.)

If you do wear glasses, then unless you're prepared to pay top dollar, for a Zeiss Victory FL, it's a good idea to consider an 8x42 binocular.

Copyright 2007 Michael and Diane Porter