Comparing Birding Binoculars
by Michael Porter
(Excerpts from a 1995 article in BirdWatcher's Digest)
Birding and binocular technology have evolved together. Before the modern binocular was invented, often the only way to see a bird well enough to identify it was to shoot it. Field ornithologists studied the bird in the hand, because the bird in the bush was too hard to see.
Binoculars changed all that. They made it possible to observe birds alive and wild, without harming them. Now, millions of people are able to enjoy watching birds. All because bright, lightweight, and relatively inexpensive optics have magically extended our ability to see.
Today's birder has more binocular choices than ever before. And while it's wonderful to have so many options, it can also be a little intimidating. Buying a pair of binoculars is an important and expensive decision, and you want to get it right. After all, what other material possession will you depend on so often and carry so close to your heart?
This article will help you choose the binocular that's right for you. The bottom line is that the best birding binocular is a custom fit. Often the most important factors are the personal ones, such as how a binocular fits your hands, how much power you can hand hold, and how much weight you can carry comfortably.
Our field testing
I also set up testing stations. One station let people measure how close the binoculars would focus. Another was a bean-bag rest where two binoculars could be set side by side and focused on an optical resolution chart. The viewing target was a USAF 1951 Test Pattern chart obtained from Edmund Scientific Company. It shows a series of progressively smaller squares, each made up of three lines. With the binoculars supported on a rest, you focus as sharply as you can and determine the smallest square in which you can see the individual lines. The same pattern occurs numerous places on the chart so that the resolution at the edges of the image can be compared to the resolution at the center.
Field test results
It became clear that we were looking at the resolution limit of our own eyes. This varies from individual to individual and does not improve with age. However, there were some young, teen-age eyes at the field tests, and though they could resolve smaller details, they got the same relative results when comparing two models as did their older comrades. The interesting conclusion is that the on-axis resolution of most decent binoculars exceeds the ability of most eyes to see it.
The resolution at the edges of the image, called off-axis resolution, was a different story. Here resolution differences were more apparent. This is where the top-end optics excel, and it's probably one of the main reasons people consistently preferred the most expensive binoculars.
Of course, resolution is only one factor that affects the perceived image quality. Brightness, contrast, color accuracy, the width of the field of view, how much of the image you can see with your glasses on - all these elements affect the subjective experience. So many factors interact that truly objective comparisons may be impossible. This is why there is a continuing dialog among experienced birders about which binoculars are best. And it's why your personal experience looking though binoculars must be the ultimate test.
The questionnaire results
When you're ready to purchase, there is one important rule: try before you buy. The more time you spend handling and looking through the binoculars before you buy them, the likelier that you'll make a decision you'll be happy with.
If you can find a dealer who will let you return or exchange the binoculars, that's ideal. If a friend or someone in your local birding organization owns the model you are considering, talk to that person about the binoculars. He or she might even offer to let you try them out.
Checking for alignment
Here's a quick check for mis-alignment that you can do yourself. Look through the binoculars at a horizontal line, such as a telephone wire. Slowly move the binoculars away from your eyes until you see two images instead of one. The horizontal line should stay lined up. If the line appears higher in one circle than the other, the binoculars should be repaired.
My personal favorite (in 1995) and why
The focus knob is a long knurled cylinder, easy to find and use, even with gloves. It is slightly recessed for protection. The close focus is 13.2 feet, and the adjustment is silky smooth. The diopter adjustment, on the front of the focus knob, is easy to see and use, and it locks in place.
The eyecups don't roll down, but push in or pull out in an instant. At the front of the bridge is a tripod mounting thread, a feature missing from many binoculars.
The design is exceptionally rugged, both inside and out. The soft, polyurethane armored shell is pleasant to touch and gives a non-slip grip. Completely waterproof and nitrogen filled, the binoculars will withstand immersion in water and won't fog up internally in humid weather. The lens protection system is the best-integrated design I have seen. The rain guards sleekly match the shape of the eyepieces and snug down neatly. Small lens covers slip inside the barrels to protect the objective lenses. These attach cleverly so that they pop off instantly but don't get lost. The system is so well thought out these binoculars do not need or even come with a case.
To underscore Swarovski's confidence in their design's ruggedness, they introduced a lifetime warranty program in 1995 that will fix anything that ever happens to them. It's limited to the original owner but other than that seems to cover everything except loss or theft.
Their only drawback is that they weigh 33 oz., which may be too heavy for some people. If you want 10 power, there is an almost identical 10 x 42 model that weighs 30 oz. There is also an 8 x 30 model that weighs only 19 ozs.