A Guide to Low-Light Binoculars

By David Peterson
Published on May 1, 1989
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You'll find extra hours in your nature-watching day with the right optics. 
You'll find extra hours in your nature-watching day with the right optics. 
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Most binoculars are either roof prism (right) or porro prism (left).
Most binoculars are either roof prism (right) or porro prism (left).
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The field of view of roof prism binoculars extends 341 feet wide.
The field of view of roof prism binoculars extends 341 feet wide.
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Porro prism binoculars have a 394-foot field of view.
Porro prism binoculars have a 394-foot field of view.
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Compact 5X32 binoculars trade some relative brightness for convenience.
Compact 5X32 binoculars trade some relative brightness for convenience.

It’s at least a thousand yards across the river valley to the grassy little park where I watch our local elk feed most every June evening. Tonight they emerge from the quaking aspens and scrub oak at exactly 7:30, following the lengthening tree-shadows out into the little clearing.

By 8:40, it has grown too dark to continue watching the animals through my little 7X2 minibinoculars. In fact, I can no longer see well enough through them even to focus. I put the minis aside and take up a newer, larger pair, of low-light binoculars, size 7X50.

Optical magic.

Not only are the elk once again visible, but with the help of the big 7X50s, I can now make out subtle differences in size and coloration between individual animals and observe exactly what each is doing: A lone cow is lying near the bottom edge of the park chewing cud. A few yards above her, next to a clump of scrub oak, lies a second, somewhat larger cow, this one with a very small calf relaxing nearby. At the very back of the clearing, two pony-sized yearlings are playing tag in and out of the “quakies.” A sixth animal is feeding in the deep shadows

With these magical low-light binoculars, a full half-hour passes before I again lose clear sight of the little herd. That’s half an hour of prime-time nature observation I would not, could not, have enjoyed without them.

Since wildlife is most active (and thus most visible) at dawn and dusk, serious watchers need binoculars with the ability to magnify not just images but ambient light as well–field optics that will provide rewarding viewing not just in good light but also in the deep forest shadows of midday and at the dim edges of early morning and late evening. Unfortunately, the minibinoculars so popular today, even the very best of them, actually reduce the amount of light reaching your eyes, while most popular-sized binoculars enhance image brightness only very slightly, if at all.

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