Binoculars are a great way to see further into the distance and are popularly used by nature enthusiasts to observe birds and other wildlife, as well as by theatre goers and sports fans. Not all binoculars are the same, however, and they vary with regards to optical capability and quality.
Binoculars are composed of two separate telescopes, with one used for each eye to give binocular vision. Binocular vision has advantages over the view provided by a monocular, or one telescope, as it is three dimensional with an accurate impression of depth. This enables users to clearly see and focus upon distant objects. It is more comfortable to use both eyes for viewing objects, and binoculars are also easier to hold in a stable and comfortable position than monoculars.
Binoculars use lenses to capture and transmit light, magnifying distant objects, and prisms to reduce the length of binoculars and orientate the image properly. To focus upon an image, binoculars have controls both in the centre and on individual eyepieces. The two basic types of binoculars are roof prism and porro prism binoculars, which vary in the way light is transmitted.
Binoculars range in size from small opera glasses to large models requiring a pedestal, though typically they are small and lightweight handheld designs. They have many different applications, from observing birds and wildlife to watching theatre and opera performances and sports events. Binoculars are used in professional environments, for example, by scientists and the military.
There are several considerations when it comes to buying binoculars. These include the type of binoculars, how much magnification is required, and what diameter objective lens is required.
Roof Prism and Porro Prism Binoculars
The two basic types of binoculars are roof prism and porro prism. They each transmit light in different ways. Roof prism binoculars have a compact, streamlined shape like an H. Prisms reflect light four times, making for a longer and more complex light path that necessitates the use of higher-quality glass and other components. The lenses and eyepieces are in a straight line and the tubes are joined around the centre. Roof prism binoculars have silvered surfaces, which results in less bright images. They have a more complex prism system, which is less susceptible to damage. Moisture and dust are less of a problem as they generally have better seals. They are also more expensive than porro prism binoculars, all other factors being equal.
Porro prisms have a traditional design with an M shape. Two prisms at right angles reflect light three times. The lenses and eyepieces are not in a straight line, but are offset. The lenses are usually further apart than the eyepieces, though in some models, they are placed closer together with the eyepieces further apart. Their design means that they are typically larger than roof prism binoculars. The focusing system, using eyepieces to move in and out, is more susceptible to wear and can easily become misaligned. However, they are also typically superior in image quality, producing more highly magnified, brighter images with more depth. They are relatively inexpensive. Both roof and prism binoculars have advantages and disadvantages, and both are popularly used.
Magnification is expressed by a number followed by an x sign, for example 8 x. This appears in front of another number which gives the objective lens diameter. The magnification number indicates how much closer the object will appear than without using binoculars. So binoculars with a magnification of 8 x will magnify the object by eight times, making an object 80 metres away appear 10 metres away, for example.
How much magnification is required depends on what the binoculars are to be used for. Binoculars with a higher magnification also have a narrower field of view, which can be helpful for viewing fixed objects far away but is less helpful for watching team sport events or horseracing, or even locating birds. The higher magnification can, however, reveal more detail, so deciding upon magnification sometimes involves a compromise between convenience and breadth of view and detail.
The two most common magnifications are 8 x and 10 x, with 8 x offering a wider viewing angle and 10 x offering higher magnification. Beyond 10 x it can be difficult to use binoculars without a tripod, which limits their uses and convenience. Some people find even a 10 x difficult to hold steady, so try one out before buying if unsure.
Objective Lens Diameter
The number after the magnification is the objective lens diameter, measured in millimetres. The objective lenses are those at the end of the binoculars, where light enters, whereas those in the eyepieces are called ocular lenses. Binoculars with a larger objective lens diameter can allow in more light and produce a brighter image. They are useful for low light conditions. However, this also makes them larger and heavier. Binoculars are sometimes referred to as standard sized and compact binoculars. Compact binoculars typically have objective lens diameters of less than 30mm. Standard-sized binoculars range from 30 mm to around 50 mm.
Other considerations when purchasing binoculars include their size, whether they are required to be waterproof and, for people who wear glasses, the binoculars’ eye relief.
Size is dependent upon several factors, including whether they are roof prism or porro prism binoculars and the objective lens diameter. It is an especially important consideration if the binoculars are to be used frequently on the move or taken away on holiday. For example, check if they need to be carried in hand luggage or carried in a pocket or around the neck.
Binoculars may need to be waterproof if they are to be used frequently outdoors in wet weather or high humidity. Using non-waterproof binoculars in these conditions could cause damage from water ingress.
The binoculars’ eye relief is the distance the eyes can be from the eyepiece without losing any information. This is important information for people who wear their glasses with binoculars. Typically eye relief should be more than 14 mm for glasses wearers, though people with thicker glasses may need more.
Binoculars can be an expensive purchase, so buying a used pair can be a good option. It is possible to buy a pair of high-quality used binoculars for the same price as an inferior pair new.
The usual kinds of considerations apply when purchasing used binoculars as with other optical or photographic equipment, or indeed any used items. Buying from a reputable seller with solid feedback is always a good idea, and they should provide a thorough product description, answering any further queries if need be. Compare the price with that of other binoculars, the same model if possible.
The description should be accurate and provide details of any wear or damage, including cosmetic damage. Photographs can be useful here. Check for scratches on the lenses and any damage to the body or case. Bear in mind that some problems are more common with some types of binoculars than others, for example, porro prism binoculars are more prone to both misalignment and moisture ingress than roof prism binoculars. Used binoculars may or may not come with the case, but it’s a good sign if they come with a decent case. As well as used binoculars, there are also binoculars for sale that have been refurbished, either by the manufacturer or the seller.
Binoculars are devices composed of two separate telescopes used for viewing distant objects. They range significantly in size, though most consumer binoculars fall into either compact or standard sixed categories. There are two basic types of binoculars – roof prism binoculars and porro prism binoculars. Both use prisms to reflect light along the length of the tube, but they do this in different ways, with roof prism binoculars using a more complex system. Roof prism binoculars tend to be more compact and streamlined, and they are less prone to damage from wear and moisture ingress. Porro prism binoculars are cheaper, due to their simpler optics, and are capable of producing brighter, higher-quality images. Binoculars also come in different magnifications, with 8 x and 10 x standard magnifications. 8 x binoculars are useful for watching team sports and birdwatching as they provide a wide field of view, while 10 x are useful for revealing fixed objects in high detail. Binoculars also come with different-sized objective lenses, with larger objective lenses more suitable for low light conditions. Other considerations when purchasing binoculars include waterproof and eye relief requirements. When buying used binoculars, bear in mind standard considerations such as seller feedback and reputation, product description accuracy and thoroughness and any potential damage or problems. Buying a pair of used binoculars can be an excellent option if on a budget.