Binocular PrismsA prism is a transparent object that admits light but causes the rays to get bent or shifted. These let you see a correctly oriented image when you look through a pair of binoculars. Prism binoculars employ prisms in the optical system to rectify an inverted image projected by the objective. The prism also…

Phase CorrectionPhase correction is a set of coatings on the prism glass that keeps light in correct color phases. These coatings are only needed on roof prism binoculars to enhance resolution, contrast, and color fidelity. Roof-prism binoculars split the light entering the barrels into two separate paths. After passing through the objective lens, the light…

Objective LensesThe objective lenses of binoculars are the front lenses. The diameter of one of these lenses, given in millimeters, will be the second number describing a particular binocular. Hence, a 7×42 binocular has an objective lens of 42mm. The diameter of the lens determines the light gathering ability of the instrument, with the greater…

Magnification is the degree to which the object being viewed is enlarged. Magnification is one of the very important reasons why most people buy a pair of binoculars. The common binocular magnifications are 6x, 7x, 8x, 9x, and 10x. The exact magnification that a binocular provides may be calculated from the focal length of the…

While binoculars have maintained the same basic structure over the years, modern technology had enabled advancements in the area of lens coating, which has meant better light transmission and thus greater clarity, especially in higher-end binoculars. All binoculars worth considering today should be coated. Coating the lenses guards against unwanted reflection and transmits as much…

Glass QualityThe optical glass used in a binocular is the only part that directly affects the image quality you see through your binocular. The objective lens of a binocular refracts or “bends” light, attempting to direct that light to a certain focal point at some distance behind the lens of the binocular. Each color or…

When you’re in the market for binoculars, you’ll soon find that each model is described with two numbers, the first being the magnification, or “power,” and the second referring to the diameter in millimeters of the objective lens (the aperture). For example, 10×50, 7×35 or 8×42. Simply put, for example, a 7x pair of binoculars…

Field Of ViewThe field of view is the area seen through your binoculars. It is properly measured in degrees. The larger the field of view the more area you can see. Field of view is particularly important when observing moving subjects, like animals or birds, or at sporting events. If a binocular has a field…

Eye Relief Binocular Eye relief is the distance behind the eyepiece lenses at which the image is in focus, and indicates how far the binoculars can be held from your eyes and still allows you to see the entire apparent field of view. In general, the longer the focal length of an eyepiece, the greater…

Exit Pupil BinocularIf you divide the objective lens diameter by the magnification, you will get a number approximately between 4 and 8. This number is called the exit pupil, and represents the diameter of the beam of light that leaves the eyepiece when you hold a binocular with the objective pointed towards a light source.…