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Mid-sized Binoculars Review
How We Scored the Binoculars

by Michael and Diane Porter

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What did we study?

We scored the binoculars in four categories: optical resolution, focus knob, diopter adjustment, and fit-&-feel. We mapped the scores such that 5 was the highest score in each category. The scores are relative and limited to the binoculars in this study, and it would be incorrect to try to compare these numbers to those in previous studies. These scores appear on The Chart.

The chart also includes data from each binocular's specifications, as well as the street prices. The weights are our measurements, using an electronic postal scale. All binoculars in the chart are described by their manufacturers as waterproof. To keep the chart a reasonable size, we left out some manufacturer's specs, such as the type of glass, since the resolution scores already reported the optical result.

The Overall Scores are a mathematical calculation that includes optical resolution, focus knob, diopter adjustment, fit-&-feel, and field of view, with the greatest emphasis on resolution scores. The Overall Scores do not incorporate price, weight, size, close focus, eye relief, or prism style, since these are considerations of personal preference rather than of quality. For example, eye relief matters only to glasses wearers, and the relevant data is in the chart.

As we performed the resolution tests, we also looked for chromatic aberration, which showed up as color fringing at the edges of high-contrast graphics. The correlation between high resolution scores and freedom from chromatic aberration was very strong.

Fit & Feel

Fit & feel are personal, but some aspects are universal. Strap lugs shouldn't poke your hands. The binocular should balance naturally. The coverings should be non-slip, should protect the binoculars, and should feel pleasant against the skin. Any ridges or indentations should work with various sizes of hands. Most importantly, a binocular should fit your hand so that you instinctively grasp it the same way each time. This is crucial to getting on the bird quickly.

In all target sports, good aiming technique is based on developing delicate and repeatable kinesthetic memory. In Eugen Herrigl's book, Zen and Art of Archery (a best seller for more than 50 years), the Zen archer can hit targets even in the dark because his muscles remember where the target is, and he holds the bow and arrow in a consistent way every time. Aiming a binocular also depends on holding the binocular consistently, so that when you bring it up to your eyes, you are looking exactly where you intended.

Seconds count in birding. How long it takes to find and focus on a bird makes the difference between getting that life bird and telling yourself how it really doesn't matter--you had a good time outside enjoying nature today anyway.

Focus Knob

We rated focus knobs on smoothness, proper resistance, and how easy they were to reach. We checked for looseness or backlash that could make fine focusing difficult. We did not rate speed of focus, because all the binoculars we tested were within the range of personal preference. But after trying to achieve perfect focus a zillion times during testing, we personally came to prefer slower focusing knobs.

Diopter adjustment mechanism

A binocular's diopter adjustment allows you to compensate for focusing differences between your right and left eyes. You set the diopter by focusing each eye separately on a subject at the same distance. Once you determine the proper setting for your eyes, you can leave it there. However, if you loan your binocular to a friend, or the setting gets changed, you have to re-set it. Setting the diopter is easier with some binoculars than others. Good diopters are easy to adjust and have a marked scale. They also lock so that they can't be accidentally changed. The mechanism is usually located on the right eyepiece or, better yet, actually uses the focus knob.

Focus knob diopter vs. eyepiece diopter

The focus knob solution lets you pull the knob out and use it to focus only one eye. You focus using the same knob and finger skills as usual. This makes the adjustment ergonomic, natural, and fast. When finished, you push the knob in, and it clicks back into place and locks the setting so that it can't be moved by accident.

The other style of diopter employs a ring that you turn on the right eyepiece. Eyepiece diopters without locks are often designed to be hard to turn, to prevent accidental changes, but this makes them difficult to use.

NEXT: Binoculars of Note

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