When I first realized how much I enjoyed birding, I knew I needed some new binoculars. I owned a pair of Bushnell porro prism binoculars at the time. Porro prisms are the ones that have a ‘z-shaped’ optical path, where the objective lenses are offset from the eyepieces. These are the kind of binoculars favored by Navy admirals, or at least by the actors playing them, when they scan the sea for U-boats. They usually have a lot of magnification and weigh almost as much as an anvil. And they’re nearly useless for birding. So, I knew I wanted the other kind, called roof prism binoculars, where the objective lenses are in line with the eyepieces, giving you a lighter-weight streamlined shape. Unfortunately, I still thought I needed a lot of magnification, so, I bought a pair of 12 X 50s. The first number is the magnification, and the second number is the diameter (in millimeters) of the objective (front) lens. The magnification number basically tells you how much closer an object appears than without magnification, so, 12 X 50 binoculars ‘bring’ an object 12 times closer.

The second number, objective lens diameter, relates to light-gathering capability. The larger the number, the more light is gathered, and the more light that is gathered, the brighter the object becomes. One would think, then, that you should look for the biggest numbers available, both in magnification and in objective lens size. However, big numbers are not the whole story, and lots of magnification and big lenses have their shortcomings, especially when it comes to birding.

For one thing, bigger numbers generally mean bigger binoculars, and a 12 X 50 pair, as I quickly learned, weighed enough to take a lot of fun out of birding. Higher magnification also gives you a smaller field of view, something you do not want when birding. When your friend spots a rare warbler in a mesquite tree 40-feet away, you want to be able to ‘get on’ the bird quickly, but with a smaller field of view you might still be trying to find the bird long after it has flown the coop.

Larger magnification binoculars also take more time to focus. When you’re birding, you want to be able to bring a bird into focus quickly. Some birds cooperate by sitting in one place, but the most exciting ones always seem to think the grass (or tree) is greener somewhere else. Sometimes birds land close by, and your birding binoculars should focus on birds as close as ten feet, uncharacteristic of those with larger magnification.

For most of us on Social Security, a steady hand is a distant memory. For this group, even a 10X pair of binoculars will exaggerate an unsteady hold. Birders have found that 7 or 8 magnification is ideal in terms of weight, field of view and ability to hold it steady, so you should limit your choices to 7X or 8X magnification. The second number on binoculars is the objective lens size, which is divided by the magnification to calculate exit pupil size, and this number should approximate the size of a human pupil, which ranges from 4 millimeters (daylight) to 7 millimeters (low light). The most popular birding binoculars are sized at 8 X 42, which calculates an exit pupil size of 5.25, ideally within the human pupil range.

Binoculars come in many flavors, at a wide range of prices. If you have one of those pair that Sterling Hayden used to spot German submarines, or if you are trying to find birds with a compact pair of opera glasses, it’s probably time to trade up. The good news is that it’s not necessary to buy the most expensive binoculars around. There are some beauties at $2,000, but you can find excellent high-performance binoculars for $500 or less. If you are serious about birding, you probably should avoid binoculars under $100, since these are less likely to have good optics.

The latest binocular review from the Audubon Society (2019) lists three top choices at $500 or less: Zeiss Terra ED 8X42 at 24.5 ounces ($500 on Amazon), Nikon Monarch 7 8X42 at 22.9 ounces ($437 on Amazon) and the Vanguard Endeavor ED 8X42 at 25.8 ounces ($284 on Amazon). The nature shop at Tucson Audubon often will match online reseller prices such as Amazon for members, and they waive the sales tax, just one of many reasons to consider joining Tucson Audubon. In addition, the above binoculars come with a limited lifetime warranty, a feature that provides near free return and repair (or replacement) service by mail.

If you have questions or comments about SaddleBrooke’s birds, or to receive emailed information about bird walks led by Bob and Prudy, call (520) 825-9895 or send an email to bobandpru@gmail.com. Previously published articles can be found at www.birdingthebrookeandbeyond.com.


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