A decent pair of binoculars at the helm of any boat can prove to be a valuable piece of equipment and make the captain’s job just a little bit easer. But with so many options out there and prices ranging from inexpensive to seeming outlandish how do you choose which would be right for your application? The truth is there is probably a pair of binoculars that would work well for you in all price ranges and knowing what makes a good pair better than others is not rocket science.
The ideal pair of binoculars aboard would one that is easy to hold and is not heavy but has a good ‘feel’ to it and is easy to hold steady. You want a pair that can hold up to the wet and damp environment aboard and will not fog or mildew internally. You will need a pair that is fast to focus and allows a wide field of view, making it easy to pick up targets even in rough seas. It should work well in low light and allow lots of light in. If you wear glasses the binoculars need to be comfortable to use and easily adjusted to your face and glasses with the ability to adjust to your individual vision. Lastly, but certainly not least in importance, they should be clear and crisp and allow great contrast on the water. If you have all these features you have a great pair of binoculars.
The physical characteristics of the binoculars are important. They can be made of many different types of materials, with chassis made up of composite materials, plastics, alloys, aluminum and even brass. A well-made pair will feel substantial in your hands no matter the physical size of the binoculars. They are available in full-size frames, mid-size and compacts. Even a quality pair of compact binoculars will have a good feel to them, with the combination of the frame and glass optics making up the bulk of the weight. The outer coating should feel good to the touch and be a graspable in wet conditions. When your hands are cold and wet you want to be able to hold on firmly and steady your view.
Obviously magnification is important. The first number in the description of a pair of binoculars is indeed the magnification. For example a 7 x 50 pair has a magnification of 7, or it will magnify what you are looking at 7 times greater than what you would see with the naked eye. In 8 x 20 would have a magnification of 8 times greater. One would think that a higher magnification would be better, but you should keep in mind that if the magnification is too high it may be difficult to stay focused or locked on to a target in a moving boat – the object may keep dropping out of view. Most popular marine binoculars on small to medium sized vessels tend to fall in the 7 or 8 times magnification for that reason. An exception would be image-stabilized binoculars, such as those offered by Canon, Fujinon, Nikon and Fraser Optics. These have an internal stabilization mechanism that allows for a much higher magnification with little movement. They also come with a much higher price tag.
The second number in a binocular description is the size of the lens at the far end of the binoculars farthest away from you when you hold them up to your eyes. This is known as the objective lens and is measured in millimeters. A 7 x 50 binocular has a magnification of 7 times and a 50mm objective lens. This measurement is important as a larger objective lens translates to the binoculars letting in more light. You can figure out the relative brightness of a pair of binoculars by dividing the objective lens diameter by the magnification and squaring the answer. A 7 x 50 pair would thus have a relative brightness of just over 50, where and 8 x 20 pair would only be around 6.25 – a big difference in low light. Another way of determining relative brightness of a particular pair of binoculars is by squaring the exit pupil. When you take your binoculars and hold them away from your face a foot or two you see a small circle of light in the lens that would normally be against your eye, the diameter of that circle in millimeters being the size of the exit pupil. As with the prior method, the higher the number the brighter the binoculars in lower light.
Of course the quality of the lenses, lens coatings and the internal prisms also play a factor in the quality of the image you see through the binoculars. Porro prisms are found in traditional binoculars and roof prisms are found in compact tube type binoculars. The prisms can be of either BK-7 or BAK-4 verities. BK-7 are made up of a boro-silicate glass but BAK-4 prisms are made up of a denser, finer glass that helps reduce light scattering and creates a sharper image, but it comes at a higher price. Roof prisms can allow binoculars to be more compact and lighter by their construction but can be more difficult to manufacture, thus driving cost up on them. Various coating on some or all of the lenses or sandwiched between them can make huge differences in contrast and glare and should also be considered. Focus can be a fixed focus, such as found on Steiner binoculars where the entire range of view is in focus or center focus with a focusing wheel. Binoculars also will have individual adjustments for each eye to compensate for differences between the eyes and differences in distance.
Having a built-in compass and range finder is also possible on some marine models of binoculars. With this feature you can determine range and distance easily without having to use a hand-bearing compass. It is certainly a nice feature to have when navigating. Compasses can be electronic or magnetic depending on model. All will give you information displayed within your field of view as you look through the eyepieces.
The best way to be sure a pair of binoculars is right for you is to try it out. By doing your homework and the math described you can get a good idea on how it will perform, including in low light, but there is nothing like putting it up to your eyes and comparing models. By selecting a quality pair you will assure yourself years of pleasurable viewing.