How to Choose Binoculars

Choosing the right binoculars can be a complex and confusing process given the many options available. While the perfect binoculars depend on individual preferences and needs, understanding these specifications will help you make an informed choice. To help simplify this decision, consider the following key factors. 

The View

Power (Magnification) Higher magnification allows you to see objects more closely and in greater detail. However, it also makes the binoculars harder to hold steady, reduces the field of view, and decreases the apparent depth of focus. Although there are techniques to stabilize binoculars, even a 10x magnification can be challenging for some users.

Field of View  Field of view, measured in feet or meters at 1000 yards or meters, indicates the width of the visible area. A wider field of view makes it easier to locate birds but may reduce the ability to resolve fine details. Generally, lower magnification results in a wider field of view, but factors such as eye relief and close focus can also influence it. Too wide a field of view may cause image distortion at the edges.

Exit Pupil The exit pupil size, calculated by dividing the objective lens diameter by the magnification, determines the brightness of the image. Larger exit pupils (e.g., 7mm in 7x50 binoculars) provide brighter images and are easier for your eyes to align with, especially in bright conditions when your pupils are contracted.

Eye Relief Eye relief, the distance behind the ocular lens where the image is in focus, is crucial for eyeglass wearers. Longer eye relief (typically at least 15mm) allows eyeglass wearers to see the full image without removing their glasses. However, longer eye relief can also reduce the field of view.

Close Focus Close focus refers to the shortest distance at which binoculars can clearly focus. Birders and butterfly enthusiasts often need binoculars with a close focus of 10 feet or less. High-quality birding binoculars can focus as close as 3 feet, making them ideal for observing nearby wildlife.

The Glass

Objective Lenses Objective lenses gather light; larger lenses capture more light, enhancing image detail in low-light conditions. For example, a 50mm objective lens collects 42% more light than a 42mm lens, doubling the light intake of a 35mm lens. This increased light gathering ability is essential for quality birding in various lighting conditions.

Prism Glass Binoculars use either BK-7 or BaK-4 prism glass. BaK-4 prisms, made with barium, are superior and more expensive than BK-7, which uses boron. High-quality binoculars usually specify BaK-4 prisms.

Coatings Lens and prism coatings reduce internal reflections and correct light wavelength focusing. Various coating levels enhance image quality but also add to the cost. The benefits of these coatings are detailed in the All About Optics section.

The Body

Body (Prism) Design There are two primary designs: Porro prism and roof prism. Porro prism binoculars are cheaper but heavier and harder to weatherproof. Roof prism binoculars are lighter, more durable, and easier to weatherproof, though they are more expensive.

Weight Weight impacts comfort during extended use. Heavier binoculars can cause fatigue, but they also tend to be steadier. Modern materials allow for durable yet lightweight designs. Balance is more critical than weight; well-balanced binoculars minimize strain on your arms, wrists, and hands.

Ease of Focusing A good focusing mechanism is quick and precise. Ideal binoculars transition from close focus to infinity within a full turn (360º) or less. Some binoculars feature variable speed focusing gears, providing slower focus close in and faster focus at longer distances. Depth of focus and focusing speed are crucial for achieving a sharp image.

Eye Cups Eyecups prevent stray light from entering and help maintain the correct distance between your eyes and the lenses. Modern eyecups twist up and have click stops at regular intervals, making them adjustable and durable.

Protection

Weatherproofing Weatherproofing ranges from basic protection to full nitrogen-purged waterproofing. For active birders, nitrogen-purged waterproofing is recommended, as it prevents moisture, dust, and other contaminants from entering the binoculars.

Armoring Armoring, usually synthetic rubber, protects binoculars from physical damage and corrosive elements. Investing in well-armored binoculars ensures long-term durability and reliability.

Conclusion

At Optics4Birding, we aim to answer your questions and guide you through the essential factors for selecting the right binoculars. By reviewing popular products and providing unbiased information, we help you make the best choice for your nature observation needs.