Also commonly referred to as "power", magnification is a measure of how much closer an object appears when viewed through the instrument. For example, a 10x binocular will make an object appear 10-times closer than it would normally appear. An object positioned 100 yards away would appear as if it was just 10 yards away in a binocular with 10x magnification. The human eye is considered 1x magnification.

The edge-to-edge angular diameter of the image displayed in a binocular as seen by the eyes of the observer. It is an inherent specification for a given binocular design. The "angular diameter" of an object is defined as the angle an object makes (subtends) as seen by an observer.

The diameter of the circle of light exiting the binocular. Exit pupil is calculated by dividing the objective lens diameter by the binocular magnification. For example, a 10x50 binoculars has an exit pupil of 5mm (50/10=5). Knowing the exit pupil of a binocular can help determine the optimal binocular fro your needs. If a binocular exit pupil is larger than the dilation of the user's pupil, resolution is reduced since the maximum amount of light is not entering the eye. Typically under true dark adaptation a healthy human eye will dilate to approximately 7mm. This number can decrease with age and health factors.

Binocular lenses and prisms are often coated with anti-reflective material to minimize light loss as light travels through the multiple optical surfaces of a typical binocular. Coatings help maximize the amount of light transmitted through each glass surface of a binocular, so as much light as possible reaches the observer's eyes to provide a bright and sharp image.

Good lenses are at least "fully coated," with a single layer of magnesium fluoride coating applied to each air-to-glass lens surface. Multiple layers of coatings are even more effective; the term "multi-coated" means one or more air-to-glass lens surface has multiple coatings. "Fully multi-coated" optics are even better, meaning all lens surfaces have multiple layers of anti-reflective coatings applied for maximum light transmission and optimal image quality.