Binoculars bring subjects into focus. What can be unclear, though, is choosing the best binoculars for your viewing needs. Start with these specs and this buying guide.
Magnification/Lens Diameter
The binoculars’ name provides two important pieces of information. The first number is the level of magnification. Canon’s 10x32 IS binoculars, for example, magnify at 10 times. An object will appear 10 times closer to you than it would to your unassisted eye; that is, something 100 metres away will look 10 metres away. The second number indicates the objective lens effective diameter (or brightness), in millimetres. Smaller diameter binoculars are lighter and more portable; larger diameters are bulkier but let in more light and provide a brighter view. Both measurements also appear on their own in the specs.
In addition to a pair of numbers, you will see two letters in the name of every pair of Canon binoculars. IS – short for image stabilization – helps cancel out shaking from movement and vibration to provide a steady viewing experience. With Canon IS binoculars, you can manually switch between modes: Normal, for tracking subjects in motion; and Powered, for focusing in one direction.
Field of View
Some specs include as many as three “field of view” entries.
Real Field of View: The view through the binoculars measured from the centre of the objectives lenses, expressed in degrees.
Apparent Field of View: The angle of the magnified field of view through the binoculars; anything greater than 60 degrees is considered a wide field of view.
Field of View: The width of the area when looking through the binoculars from a stationary position; it’s expressed in one of two ways – in feet at a distance of 1,000 yards; or in metres at 1,000 metres – and calculated by multiplying the real field of view by 52.5.
Exit Pupil
The exit pupil is the effective lens diameter divided by the magnification – i.e., the second number in the binoculars’ name divided by the first. The exit pupil for Canon’s 10x32 IS, for example, is 2.7mm (32 divided by 10). It’s how much light reaches your eyes. The larger the pupil diameter, the brighter the image the binoculars can deliver. The exit pupil should always be larger than the pupil of your eye. On their own, human pupils are about 2mm in bright environments, 7mm in dark. If you’ll be using the binoculars mostly at night or in dark settings, you’ll want a pair with a large exit pupil (5mm or more).
Eye Relief
Eye relief refers to the distance away from the eyepiece lens at which your eye can see the entire field of view, and is an important spec for anyone who wears glasses. Glasses, by nature, move your eyes farther back from the eyepiece/ocular lens. Eye relief offsets the distance between your glasses and the surface of your eye, ensuring optimal distance between your eyes and the ocular lenses. (Eye relief also offers comfort for non-eyeglass wearers. You can adjust how close you hold the binoculars to your eyes.) If your eyes are too close to the ocular lenses, vignetting and shadowing reduces your field of vision. If your eyes are too far back, you will see only the centre of an image and not the outer edges. Built-in eyecups that either fold down or rotate up and down let you adjust to the distance that allows you to see the entire field of view.
Closest Focusing Distance
Binoculars are not just for getting a closer look at faraway objects. You may want to magnify something only a few feet away, such as the markings on a bird or the brushstrokes of a gallery painting. This spec indicates the shortest distance where focusing is possible.
Pick a pair with low magnification, 8x or 10x. As magnification increases, the field of view narrows. A larger field of view is ideal for tracking subjects like a bird in flight.
Bigger is better here. Maximum magnification – 15x or 18x – lets you see into those faraway galaxies; a large objective lens lets in more light for clearer and brighter views.
You’ll need magnification no greater than 12x to enjoy field-level views from even the cheap seats. The wider field of view from lower magnification makes it easy to track both athletes and objects in motion.
Whether you use them to watch sports, stars or birds, Canon binoculars offer the pristine optics and image stabilization to meet your viewing needs.