Your Guide to Buying Lightweight Binoculars

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Your Guide to Buying Lightweight Binoculars

Binoculars are popularly used to enable distant objects to be viewed clearly and distinctly. The demand for compact and lightweight binoculars is increasing as more people discover the benefits of taking binoculars on holiday, while camping or hiking, watching the theatre or ballet, or in other situations where their portability is an important factor.

About Lightweight Binoculars

Binoculars, made up of two small telescopes, give the viewer magnified, binocular vision. The popularity of binoculars stems from their ease of use as well as their visual capabilities; portability and comfort of use being two important factors when it comes to choosing binoculars. There is a growing market for lightweight binoculars.
All binoculars work by allowing light to enter through objective lenses. The light is then transmitted via a light pathway to ocular lenses in the eyepieces. The path light follows from objective lens to ocular lens is different depending on the type of binocular, and this has important effects on the size and weight of binoculars.

Choosing Lightweight Binoculars

When choosing a pair of lightweight binoculars, it is important to bear in mind the factors that influence binoculars’ size and weight, and to weigh up the benefits of compactness and light weight against other issues such as quality, required magnification, and objective lens size.

Factors Affecting Size and Portability

Important factors affecting size and weight include binocular design and objective lens diameter. Compact binoculars will also typically offer a smaller field of view than standard-sized binoculars.

Binocular design

The two designs are porro prism and roof prism. They have different systems of prisms through which light is directed.
Porro prism binoculars have a traditional design with the eyepieces usually set closer together than the objective lenses. In compact models, the eyepieces may be further apart than the objective lenses.
Roof prism binoculars have a straight design with the eyepieces and objective lenses at equal distances apart. This gives them a slimmer shape. The tubes can often extend out and then fold neatly away.
Porro prism binoculars have traditionally produced brighter and better defined images, but advances in technology have resulted in roof prism binoculars also producing excellent images.

Objective lens diameter

The objective lens diameter is expressed in millimetres (mm) and usually written on the binoculars. It is the number given after the magnification. For example, 8x42 binoculars have an objective lens diameter of 42 mm.
Compact binoculars are defined as having objective lens diameters of less than 30 mm. For those wanting general purpose lightweight binoculars, they are a good choice.
The disadvantage of smaller objective lens diameters is that the lenses cannot capture as much light. While generally fine for daytime use, they do not perform as well as larger diameters in dimmer conditions.

Field of view

Field of view is affected by binocular size, design, and magnification. Lower magnification binoculars, larger binoculars and porro prisms typically offer a wider field of view.

Magnification

While not having a direct effect on the size of binoculars, any magnification higher than 10x will typically require a tripod, detracting from the portable nature of lightweight binoculars. Some people also find they need a tripod with 8x binoculars.
This is an especially important consideration with lightweight binoculars because their small size can make them more difficult to steady and focus. If possible, always try out a model before purchasing.

Image stabilisation

Image stabilising mechanisms help binoculars to minimise the blurring effects of higher magnification. However, image stabilising binoculars require a battery and are typically bulky and less robust than standard binoculars. They are not recommended if size and portability are determining factors.

Optical Coatings

Optical coatings can improve the light transmission and therefore performance of binoculars. High-quality coatings are increasingly being used in compact binoculars, especially with roof prism binoculars. Various coatings are used. They enable binoculars to be smaller and still produce crisp, clear images.

Anti-reflective coatings

Used on both roof and porro prism binoculars. Minimise light scattered through reflection and make the image sharper. This can make coated binoculars with a smaller objective lens better with regards to image quality than uncoated binoculars with a larger objective lens.
Fully coated binoculars have all air to glass surfaces coated once, while fully multi-coated binoculars have all air to glass surfaces coated multiple times. Coated binoculars have some surfaces coated once, and multi-coated binoculars have some surfaces coated multiple times.

Phase correction coatings

Used on roof prism binoculars. The prism design causes light to be split and polarised, causing interference and lowering resolution. Phase correction coatings are used to minimise this effect. Phase coatings may also be referred to as P-coatings.

Aluminium or silver mirror coatings

Used on roof prism binoculars. Mirror coatings capture light that would otherwise not be transmitted through the tube, being lost through total internal reflection. Silver was traditionally used but is prone to tarnishing. Aluminium is not as reflective, so high end binoculars still use silver, but they seal it in nitrogen or argon to prevent tarnishing.

Dielectric coatings

Used on roof prism binoculars. Dielectric mirror coatings are formed of several layers, each reflecting different wavelengths of light. The combined reflectivity is higher than that of aluminium or silver mirror coatings.

Conclusion

Binoculars work by allowing the transmission of light, from its entry at the objective lenses through to the ocular lenses at the eyepieces. In between are a series of prisms which reflect light, the number and design of which are dependent on binocular design. The two basic designs are roof prism and porro prism. Porro prism binoculars are typically larger and bulkier, though compact designs are available. Roof prism binoculars have a more streamlined shape, despite their more complex optics. Size and portability can be determining factors in the purchase of binoculars, and another important factor affecting size is objective lens diameter. While it may be important to have binoculars that are lightweight, binoculars with smaller objective lens diameters are not generally able to perform as well in lower light conditions. To an extent, this can be remedied by quality of design and optical elements. Coatings are used, especially with roof prism binoculars, to aid light transmission and produce clearer, higher-quality images. Fully multi-coated binoculars have the most thorough anti-reflective coatings. Phase correction coatings aid resolution and mirror coatings minimise light being lost through internal reflection. In general, lightweight compact binoculars, defined by having an objective lens diameter under 30 mm, are a good choice for everyday use. Choose high-quality compacts if they are to be frequently used in low light conditions, and consider a slightly larger objective lens diameter. Another thing to be aware of is that binocular size has an effect on field of view, with compact binoculars having a smaller field of view than standard-sized binoculars.

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