The twilight factor is the square root of magnification times objective. Twilight factor is a mathematical formula that predicts the amount of detail that can be seen in low light.

In actual tests, some premium-grade compacts with a low relative brightness are brighter than some full-size binoculars. As with exit pupil, relative brightness should not be taken too literally, since it treats all binoculars, regardless of lens coatings and optical quality as if they are the same. It is simply an exit pupil squared, so a binocular with an exit pupil of 5mm will have a relative brightness of 25. Relative brightness, like exit pupil, is a rough guide to image brightness.This refers to the efficiency of an optic, or its ability to deliver the maximum amount of the light entering the objective lens to the eye. When talking about binoculars, you may hear the term 'light transmission' thrown around. Exit pupil should not be taken too literally since it treats all binoculars, regardless of lens coatings and optical quality, as if they are the same. An exit pupil larger than 7mm is a waste of light since the human eye cannot open wide enough to accept an exit pupil larger than this. For astronomy, an exit pupil of 5-7mm is preferred. For normal daylight viewing, an exit pupil of 2.5mm or 3mm is fine. Binoculars with large exit pupils provide brighter images under very low light conditions. For example, an 8x32 model has an exit pupil of 4mm (32÷8=4).Įxit pupil is a very rough guide to image brightness. To determine the size, divide the objective lens diameter by the power. The larger the exit pupil, the brighter the image. This refers to the size of the circle of light visible at the eyepiece of a binocular. One of the numbers you will see in a specification table for binoculars is an exit pupil. The larger the objective lens, the more light that enters the binocular, and the brighter the image. The second number in the formula (8x32) is the diameter of the objective or front lens in millimeters. We do NOT recommend using binoculars with magnification over 10x without a tripod - if you go with too much magnification in a hand-held binocular, your image will be very shaky! Also, many people ask, 'How far can you see with a binocular?' We always answer, 'You can see as far your eyes can see, but the objects will seem to be closer, magnified by the power of your binoculars.' With an 8x32 binocular, the object being viewed appears to be eight times closer than you would see it with the unaided eye. The first number is the power or magnification of the binocular. 3x25, 4x30, 5x25, 7x18, 7x21, and 8x25, are great for venues such as opera, theater, and music concerts.īinoculars are often referred to as two numbers separated with an 'x'. A larger objective lens, waterproof, and rubber armor are the main features to look for in a marine and boating binocular.Ĭompact binoculars with a wide-angle are great for concert and theater viewing using a binocular. The most commonly used magnifications are 7x40 to 7x50, but 8x40 to 10x50 are also chosen by some mariners and boating enthusiasts. Since you're on the water, a high magnification binocular is not advised. Longer eye relief and a close focus are also great features to have on your bird-watching binoculars. To see more details on smaller birds at greater distances, you may opt for a 10x42 to a 12x50. The standard binocular for birding is an 8x42 binocular. The shaking of your hands is amplified by the larger magnification. At larger magnification, you will need to use a tripod to stabilize the binoculars, as the image will be very shaky if used in a standing position. For long-range shooting, such as varmint hunting, more powerful binoculars like 12x40 to 16x50 are best. Compact binoculars are easy to store in your pocket or on a strap around your neck and the wide-angle presents a good field of view.ħx18 to 10x56 binoculars are best for hunting applications. Compact binoculars are usually found at 7x25 to 10x50 ranges. General Use Binoculars - Hiking, Stadium Sports, OutdoorĬompact and wide-angle binoculars are great for outdoor activities and getting closer to the action watching sporting events at the stadium. Consider when, where, and how often you plan to use the binocular to select the right combination of features that are right for your needs. Choosing the best binoculars for your specific application can be a challenge and this guide is intended to help you understand binoculars better. Binoculars are the world's most used optical instrument, other than eyeglasses, and they have a lot of different uses.

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