Binoculars -An overview

Compact and wide angle binoculars are great for outdoor activities and getting closer to the action watching sporting events at stadium. Compact binoculars are usually found at 7x to 10x magnification ranges. 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.

7x to 10x binoculars are best for hunting application. For long range shooting, such as varmint hunting, a 12x to 16x magnification is best. At larger magnification, you will need to use a tripod or to stabilize the binoculars, as the image will be very shaky if used in standing position. The shaking of your hands is amplified by the larger magnification. Astronomy Binoculars require large apertures and power and some use of tripods.

The standard binocular for birding is an 8x42 binocular. To see more details on smaller birds at greater distances, you may opt for a 10x or a 12x magnification with a 42 or a 50 millimeter objective. Longer eye relief and a close focus are also great features to have on your bird watching binoculars.

Since you're on the water, a high magnification binocular is not advised. Most commonly used magnification is a 7x, but 8x and 10x are also chosen by some mariners and boating enthusiasts. A 42 or a 50 millimeter objective lens should be used. A larger objective lens, waterproof and rubber armoring are main features to look for in a marine and boating binocular.

Compact binoculars with a wide angle are great for concert and theater viewing using a binocular. 4x30, 5x25, 8x25 and 7x18 or 7x21 are great for venues such as opera, theater and music concerts.

Our left eye and right eye can be different in their vision and focusing capability. Therefore, to use binoculars properly, we must compensate for such a difference, and centre-focusing binoculars have an adjustment mechanism to achieve this. You can find that almost all the binoculars listed in our store have one eyepiece (usually the one on the right-hand side) which is independently adjustable with a marked scale.

To adjust binoculars, first, use a lens cover or your hand to cover the right objective lens which is on the same side as the adjustable eyepiece (note: better to keep both eyes open to avoid distortion by squinting). Look through the binoculars and use the central focusing mechanism to focus on a distant object until it is sharp and clear.

Second, transfer the lens cover to the other lens on the left, again with both eyes open, but this time adjust the focus on the same object using the adjustable eyepiece only, until it is clear. Your binoculars are now properly focused for your use. Adjust the distance between the two eyepieces so that they in the centres of your eyes (i.e., when the two cycles merge into one). You can now use the central focusing mechanism to focus on objects at different distances, but you should keep the adjustable eyepiece at the same focus setting unless it is accidentally moved or the binoculars have been used by someone else.
 

In a binocular name, the first number indicates the magnification power and the second number is the diameter of the objective lens in mm. For example, for a pair of Nipon 10x42 binoculars, it has 10x magnification (i.e., an object will be enlarged 10 times; or an object 100m away will look like 10m away through the binoculars), and its objective (front) lens is 42mm in diameter.
 

Since the objective lenses form images that are both upside down and reversed left for right, prisms are used to invert the primary image.

Porro prism and roof prism are two most frequently used systems for such a purpose. Porro prism binoculars are characterised by the eyepieces being offset from the objective lenses, while roof prism binoculars' objective lens and eyepiece are positioned in line for a more compact feature and reduced weight. Either type of prism system, properly manufactured, gives excellent optical performance.
 

Field of view (FOV) refers to the size of the area that can be viewed through the binoculars. This can be described either in degrees or in the width of the area visible (by ft. or m) at 1000 yards or 1000 metres. Given the same size of objective lens, the lower the magnification the binoculars have, the wider the FOV.
 

An uncoated optical glass lens or prism reflects about 10% of the light incident on one of its surfaces, thus allowing only about 90% of the light to pass through. Nowadays most binocular lenses are coated with invisible coverings that work to improve the amount of light transmitted from the front lens to the eyepiece. Standard full coatings can reduce the level of light reflection to about 4% or lower; and more sophisticated multi-coatings can ensure 99% or more light transmission through the lens and prism.
 

This is the distance (in mm) the binoculars can be held away from the eye that still allows the user to see the entire full field of view as designed. Binocular users who wear eyeglasses for near- or far-sightedness can remove their glasses while observing clearly through the binoculars because the binoculars can fully correct for these eye defects. However, the users with astigmatism may need to wear their glasses in order to maintain sharp imaging through the binoculars. In this case a longer eye relief will become advantageous for these users, who cannot get as close to the eyepiece.

As a rough guide, an eye relief of 10-15mm should fit most users if this function becomes necessary. However, you may not need to look for this specification because most binocular models allow the eyecup to be either folded or twisted/pushed down to enable eyeglass wearers to enjoy an improved field of view.
 

Binoculars with centre focus system use one knob in the middle of the binoculars to move both lenses for fine focusing precision. This allows you to follow the action and switch from one object to another quickly. Binoculars with centre focus normally have one eyepiece (often the one on the right-hand side) which is independently adjustable to accommodate any difference between the two eyes.
 

One of the most important factors affecting the image brightness is known as Exit Pupil, which is a bright circle visible when the eyepiece array is viewed about 10 inches away from the eyes. A larger Exit Pupil gives a brighter image. The value of Exit Pupil (mm) = Objective Lens Diameter / Magnification Power. So, for a pair of 10x40 binoculars, its Exit Pupil is 40/10=4mm. For the Nipon 10x50 binoculars, the Exit Pupil is 5mm. The larger the objective lens, the bigger the Exit Pupil, and thus the brighter the image viewed. However, larger objective lens also means heavier and bigger the binoculars' body.

Binoculars for common use such as sightseeing and birding from near to medium range, an exit pupil size of 4-5mm is considered to be adequate for image brightness.
 

Choosing a right pair of binoculars would very much depend on your main purpose of use. Here are some examples:

If you are looking for a handy pair of binoculars to carry around easily in your handbag or in the pocket, and to use it in numerous occasions such as stadium sports, indoor or outdoor concerts/plays, travel and birding, and you also want to keep the cost down, you may choose a compact model such as 8x21, 10x25 or 12x32 compact binoculars , depending on which magnification level you wish to choose. Such a model has all the functions required for these purposes and they are light in weight. These products have a unique feature with new optical coating technology (fully multi-broadband coated green lenses) which greatly reduces light reflection over a wider spectrum and increases image sharpness.