|NATIONAL PARKS QUICKLINKS|
Backpacker Magazine – March 2008
Learning a bit of jargon will help you find your ideal binoculars.
10x means the lenses magnify 10 times more than the naked eye, so an elk at 1,000 yards appears only 100 yards away.
The larger the diameter of the front lens (measured in mm), the more light it collects. That results in a sharper and brighter image, in addition to a higher relative brightness level.
The distance (in mm) your eyes must be from the eyepiece to see the entire field of view. Smaller eye relief distances can strain your vision. Glasses-wearers should seek out an eye relief of 11mm or more.
Field of view
The width (in feet) of the area observed at 1,000 yards. The smaller the field of view, the more powerful the magnification, and the smaller the eye relief.
To make top-end binoculars waterproof and fogproof, optical spaces are filled with nitrogen gas and sealed with rubber O-rings.
This index represents the quantity of light gathered by a binocular's lenses. Levels from 4 to 16 are best for daylight; 16 to 25 are optimal for dawn to dusk; anything above 25 is suitable for all light conditions.