Second to spectacles, binoculars are the most extensively used and extremely useful optical gadgets. They come in various sizes and versions, and are a necessary part of your kit if you are the type of person who is extensively outdoors and frequently travelling. However, there are also binoculars which can be used indoors, for example, theatre/opera glasses. The different types of binoculars available in the market today are ‘compact binoculars’, ‘hunting binoculars’, ‘astronomy binoculars’, binoculars for military, marine and bird watching, digital and telescopic. When you decide to buy a pair of binoculars, it is important to know exactly why or for what purpose you need them. Based on this, there are some necessary technical specifications and usage factors to know and understand which will help you pick the right pair of binoculars for your needs.
- Binocular numbers: Every pair sports a set of numbers quoted in millimeters, say 10x12mm for example, ‘10’ refers to the magnifying power – how much larger the object which you focus on will appear when seen through the binoculars. In this example, it will be magnified ten times. The second number is the diameter of the object lenses located at the other end from the eyepiece. The diameter number denotes the amount of light which will pass through the lenses, depending on the ambient source of light in the environment you are in. If you are in a low-light area or using the binoculars in the night, the object lenses need to be of a larger diameter than what you would require in a bright or daylight setting.
- Field of View: This number describes the width of the image you will see at a distance of 1000 yards. ‘Field of view’ is the ratio between magnification power and the distance between the eyepiece and object lenses. The more the magnification, the lesser will be the width of the image you can see. The field of view width is expressed either in feet or in degrees.
- Twilight Performance: This term describes how well your binoculars will perform in low light or darkness conditions. The twilight performance can be calculated by multiplying the magnifying power of the lens with the diameter of the object lenses as described in the first point above. If you were comparing the twilight performance factor between two different pairs of binoculars, the binocular with the higher number obtained when multiplying the binocular numbers is the one with better twilight performance.
- Size of binoculars: Size of a pair of binoculars determines the performance, the smaller the size the lesser will be the degree of performance. If your requirement is for a specialized function such as bird watching or astronomy, a compact pair of binoculars will not do the job; you will require a larger-sized pair.
- Light available: The lighting and environment in which you frequently use the binoculars is another important consideration. Low light or dark environments need larger object lenses and vice versa.
- Magnification power: Distance between you and the object you want to view will determine the degree of magnification required. Low powered binoculars suffice for activities such as the theatre or bird watching, but astronomy or military usage required greater magnification power.
- Focal point: This is the minimum distance required between you and the object with the latter still in decent focus, lower magnification binoculars are best for close use such as bird watching.
- Usage, field of view & price: The type of binoculars you need to buy will depend on where you will most use them – outdoors or indoors – pairs for outdoor use need to be waterproof. Field of view, as mentioned earlier is indirectly proportional to magnification power. If the former factor is critical to your usage, buy a low magnification power pair. How much you want to spend considered along with usage is also important, if it’s for general use and pleasure you can pick up a cheaper pair, but if you need it for some special application, then spending more to get the right pair of binoculars is necessary. The price can range from $10 to over $2500. The average you should be ready to spend for a decent pair of binoculars is about $250 - $300.
Follow the requirements as listed above and you should be able to get the right pair of binoculars for your use. If your usage is varied over different kinds of tasks, it is best to buy several pairs to match each specific use; one pair may not suffice across all your planned activities.