Binoculars are definitely one of the handiest things you can take along on an outdoor adventure. Whether hunting, bird watching, game spotting, or attending a concert or sporting event, binoculars bring the action up close and personal. So picking the right set of binoculars is critical to maximizing the enjoyment they bring to whatever you do. To figure out what features will work best for your particular needs, here are a few characteristics to consider.
The first thing to consider is the magnification desired. Binocular magnification power is rated by the first of two numbers, while the second number refers to the diameter of the outer, or objective lens. Binoculars listed as 10x42mm will produce an image ten times larger than what can be seen with the naked eye and have an outer lens diameter of 42mm. The lens diameter quantifies how much light will be allowed into the binoculars. Larger lenses are better for low-light situations but add more weight. Higher magnification, while important at longer distances, affects the width of the desired viewing area, referred to as the field of view, or FOV. A good rule of thumb is the higher the magnification, the smaller the field of view. For example, when watching a concert or spotting deer at a distance are you more interested in a close-up view of the desired object or a closer overall view of the entire stage or meadow? The binocular field of view rating is calculated at a distance of 1,000 yards.
Another important decision concerns what type of prism is used to correct dispersion and image inversion caused by the curvature of the object lens. If weight and compact size are considerations, a roof prism design is appropriate. Roof prisms reflect light five times and allow the light to pass straight through the binoculars, but they are more difficult to manufacture and thus cost more. Porro prism binoculars require a larger body. The light is reflected four times and exits the binoculars on a different sight line. They cost less to produce and are readily identifiable since the outer objective lens is generally located slightly above the eyepiece. Both types reverse inversion so the viewer sees the original image. Coatings on the prisms eliminate light scattering and sharpen the final image.