Throughout history, binoculars have remained the one scientific invention that has enabled millions to observe distant objects up close and clear without having to make efforts trying to get close to a get a good view. What initially started as a device to aid humans during long-distance traveling and wartime activities has transformed into a multi-purpose optical device that has since been used in both adventurous and professional capacities, such as hunting, bird watching, marine navigation, astronomy, border control, reconnaissance missions, and many more. The sudden popularity and ease of use are a result of numerous scientific studies that have been carried out by institutions and manufacturers over the years. Despite several added features, research and development studies are still a part of many optics manufacturers, such as STEINER, Leica Camera, Swarovski, Zeiss and many others to come up with more sophisticated features while keeping the cost low, so that more people can have access to premium versions for their outdoor activities.
How do binoculars work?
Binoculars fundamentally comprise two parallel telescopes or oculars that are connected by a hinge mechanism. In each ocular, light rays enter inside the optics housing through an objective lens after reflecting from the target object and form a focused and inverted image of that object inside the chassis. This image then passes through a pair of reflective prisms before passing through a series of eyepiece lenses and into the observer’s eyes. This process occurs simultaneously in both barrels and the resulting images are superimposed and processed into one crisp image by the eyes.
Different specifications for different purposes
Ever since the production of binoculars has been commercialized in the 1970s, enthusiasts and experts from all over the world have found ways to incorporate binoculars in their leisure and professional activities and the growing demand from multiple sectors prompted manufacturers to design and produce specialized devices for specific uses. Therefore, while one binocular model may be excellent for bird watching, but the same device will not be effective for use in stargazing or marine navigation. Manufacturers achieve this by modifying several inherent features of the binoculars, such as the diameter of the objective lens, type of prisms, and magnification to name a few.
The diameter of the objective lens, along with magnification power, makes up the model specification for all types of binoculars. The objective lens size is generally measured in millimeters and provides a general idea about the overall size of binoculars, since larger the objective lens, bigger will be the binoculars to contain them. But why does the diameter of the objective lens matter so much? Answer: Light. Objective lens functions just like a glass window in a dark room. Larger-sized windows will allow more light to enter the room and therefore the objects in the room will be easily visible to the observer. Similarly, a larger objective lens will absorb more light into the binocular housing, which would result in brighter and more detailed views of objects, especially in low-light conditions. Our eyes can adjust to low-light conditions after spending some time in darkness, but binoculars are static devices and if your intended objects are located in low-light situations, it is better to invest in binoculars with larger objective lens size.
Magnification power is another important characteristic of binoculars which is why it is included in the model specifications. There is an age-old myth among first-time binocular owners that greater magnification is always better. While some types of binoculars, such as astronomical and marine navigators, might require higher magnifications of up to 20x, the reality is not all binoculars require higher or similar magnification powers. Although a higher magnification may be effective in observing very distant objects, it accomplishes this feat at a price. When looking at far-away objects with a high-powered binocular, the field of view is greatly reduced and observers are only able to view objects that are stationary, such as a distant ship or a mountain peak. A moving object will be impossible to view at higher magnifications as users will find it difficult to locate and point the binoculars at the object. Binoculars with magnification higher than 10x will also be very challenging for use handheld. Usually a tripod is needed for the use of binoculars with 12x mganification or more.
Another key aspect of binoculars is the capability to be adjusted for varying object-to-lens distances. Lenses used in optics have a specified focal length, which is the location of the point where parallel light rays passing through a lens are converged or simply, focused. For a quick demonstration, if you place your finger in front of your face and continue to move it closer to the eyes, there will be a point when your eyes will find it difficult to focus and will produce a blurred image of the finger. Now, if you move your finger back slowly, your eyes will start to focus on the finger better until your finger reaches the focal point or focus when the view of the finger will become the sharpest. Although our eyes constantly adjust to effectively focus on different objects, the range of their focal length is limited. Similarly, modern binoculars feature a focusing mechanism which can be used to adjust focus when needed. A focus knob located between the optical barrels is usually provided which can be rotated clockwise or counter-clockwise until the view becomes clear. The purpose of binoculars is to enable a person to view distant objects clearly and if it does not function as intended, it is of no use. On rare instances some binoculars feature focusing separated for each eye.
Binoculars may seem simple in nature to uneducated eyes but they are far different than using a bunch of lenses in a pair of parallel tubes to magnify distant objects. Since the pair of objective lenses inside a pair of binoculars are convex, they generate an inverted image when light passes through them. A pair of prisms are employed to rectify the orientation of objects viewed through the eye-piece. The story does not end here. Prisms are also used to lengthen the light path inside the binocular housing, by which higher magnifications can be achieved without unnecessarily increasing the overall size of the binocular.
Binoculars generally come in two types of prism configurations and when you are out deciding on which one to buy, it is important to know the difference between the two, the Roof prism and Porro prism binoculars.
Porro Prism Binoculars
Porro Prism binoculars feature a zig-zag barrel since the objective lenses are at an offset from the eye-piece lenses. The term Porro is termed after its creator Ignazio Porro, who came up with the idea of internally reflecting prisms for altering the orientation of images in the 19th century. Porro prisms are a pair of two right-angled isosceles prisms that have three highly reflective faces out of the five. No light entering the Porro prisms is lost which is why the images they produce appear brighter and more spatial.
Roof Prism Binoculars
Roof prism binoculars are comprised of two parallel ocular tubes which makes them comparatively smaller and compact. While they may appear simpler than their Porro prism counterparts, the manufacturing process of angled roof prisms is more complicated. The angles of the prisms need to be accurate and a slight irregularity will result in distorted views. Since light rays are reflected six times within the prism pair, some portion of it is lost and the resulting images are not as bright as the Porro prism binoculars. There are two types of Roof prisms available on the market. Schmidt-Pechan type which is the most common one and Abbe-Koennig type which is far more rare.
Regardless of the type, the general idea behind using prisms remains the same.
Eyepiece lenses are closest to the eye and their job is to magnify the images that are formed by the objective lenses and subsequently passed through the set of prisms. Like the objective lenses, they play an important role in generating clear and focused images to the observer’s eyes. Binocular features, such as Eye Relief, the field of view, and aberration corrections depend on the eyepiece technology, therefore, intricate research and manufacturing methods go into developing eyepiece lenses for binoculars.
Binocular categories for different purposes
Ever since the use of binoculars has become more widespread, certain modifications have to be incorporated in the binocular designs to accommodate requirements from all kinds of users, for example, higher magnification, smaller close focus, low-light capability, waterproofing technique, fog-proofing, compass, compactness, lightweight design, rugged housing, tripod compatibility, and many more. Due to the addition of these features, binoculars are classified into three categories: Entry-level, mid-range, and premium binoculars. Classification ensures that customers select the right binoculars suited for their needs as expensive and high-quality devices are not suitable for amateur users.
Hunting is the most exciting activity out of all the outdoor leisure hobbies, but it requires a great deal of skill and patience, which is why it is not in the prowess of novices. Whether you are hunting in the woods with a gun or a crossbow, you must be familiar with the importance of stealth. Additionally, the hunting sport relies heavily on low-light vision capability. This is where hunting-specific binoculars come to the rescue. Some say hunting binoculars are second only to the hunter’s weapon of choice in terms of necessity. With numerous brands and products available in the market, it can sometimes be difficult for hunters to settle on a brand or product. Regardless of the make and model, there are a few principal characteristics of binoculars that will make or break your trip.
Magnification is an important aspect in binoculars and while a higher magnification might sound effective for spotting prey, it sometimes leads to binocular steadiness problems. Magnification is also inversely proportional to field of view (FOV) through the eyepiece, which is generally not desirable in hunting binoculars because a narrower FOV would require the binoculars to be constantly moved around to capture prey, which moves quite quickly and unpredictably. The focus mechanism is also one of the most important features in binoculars since it provides a way to adjust the focus for objects that are farther away or located within a 50m radius. Another essential characteristic is low-light viewing capability, which can be improved by increasing the objective lens size but it often results in an unwanted increase in size and weight of the binoculars, and carrying and taking care of bulky binoculars on rough forest terrain are not deemed comfortable by many hunters. The last thing a hunting enthusiast will need in their device is effective waterproofing and a rugged outer casing to avoid serious damage from accidental falls.
Generally speaking, binocular magnifications of up to 10x are suitable for most hunting needs. Similarly, objective sizes of 40mm to 42mm will be effective in most low-light conditions. Most common configurations of binoculars for hunting are 8x42, 10x42 and 8x56. While binoculars come with efficient focus mechanisms, there might not be enough time to waste on focus adjustment while actively pursuing animals, such as rabbits or deer, therefore, hunters prefer binoculars that do not require constant readjustments. Thus binoculars with slow focusing mechanism are most suitable for hunting.
Call it a sport or a seasoned hobby, nearly 47 million of the US population regularly heads out to the wilderness for observing unique birds, especially those that migrate from around the world during the change of seasons. This makes birding the 15th most prevalent outdoor entertainment activity in the US alone. Since birds are fearful animals and are suspicious of human beings, birders have to be careful in keeping a distance from the beautiful creatures, to avoid disturbing the rare breeds in their natural habitats. Due to fast movements of birds, faster focusing mechanisms are advised in binoculars designed for bird watching. Additionally, birds have a habit of camouflaging themselves into their surroundings, this makes it extremely difficult to observe them from a distance while identification is out of the question. Serious bird watchers always carry a pair of binoculars on their birding trips, which enables them to see crisp views of Sternidae, Albatrosses, Songbird, and other rare kinds.
Whether you have been observing birds in the wild for years or just started this hobby, binoculars are essential for bird watching. While some birders might employ spotting scopes or cameras with telephoto lenses, binoculars have remained the go-to optical devices for this fun activity since the 20th century. The next question after “which device is best for bird watching?” is “which binoculars are the right choice for all bird watching needs?” since there are numerous models available with different shapes, sizes, and features in the market.
The first feature to settle is the question of magnification power. Similar to hunting, people generally think the higher the magnification, the better will be the binoculars. While a binocular with high power will be of help in viewing birds up close, the reality is the higher you go with the magnification, the more vibrations and small movements will translate into your view. Similarly, high-powered binoculars have a narrow field of view and a larger close focus, both of which are generally not favored in bird watching binoculars. The next step is the objective’s size. A larger-diameter objective will draw in more light and therefore enable the user to observe birds even in low light situations, but rarely do bird watchers seek birds in dim lighting conditions. Also, a larger objective would mean a bigger binocular set, which can be quite heavy and bulky, none of which birders prefer in their devices since a large device would require a tripod stand to attain stabilized viewing. Although some birders prefer to carry a tripod, it is not usually preferred among the masses. Birding is a tricky sport and a larger and heavier device will tire you out faster.
For an all-rounder binocular for bird watching, experts prefer devices with magnifications between 8x and 10x, which are quite reasonable for most birding needs since they are a compromise between acceptable zoom, the field of view and minimum close focus, the latter being an over-looked feature, but very important for close observation of small birds like Hummingbird. Secondly, objective lenses with sizes between 30mm and 42mm have a larger exit pupil and draw optimum light into the optics housing for suitably brighter images and comfortable viewing experience.
Even if you have not yet used a binocular on a yacht or a passenger ship, every single film that involves journey by a boat or ship features a set of binoculars. This is how mainstream they have become since their debut in the last century. Previously travelers used hand-held telescopes for navigation in deep waters and for recognizing incoming ships and harbors from a distance, but telescopes proved to be uncomfortable and ineffective to be used frequently. Optics manufacturers identified this problem and expanded their binocular business into this sector and the decision was very well received. Nowadays, whether it is deep-sea fishing or a leisure trip on a cruise ship, binoculars are included in the backpack of every serious mariner. When it is time to choose between the varieties of binoculars for marine purposes, some key characteristics should be checked to end up with the right device for your expeditions.
Since marine binoculars are susceptible to tougher atmospheric conditions than conventional devices, they need some extra-ordinary measures to keep functioning uninterruptedly. For instance, water and fog exposure is a serious issue in a marine setting, since the air around large bodies of water is reported to have significantly more humidity than on land. Additionally, due to constantly varying temperatures, the lenses quickly fog up both internally and externally, rendering the binoculars unusable. High tides and rough weather conditions at sea can also lead to an unintentional fall of your beloved device from your hands, so they have to be build as robust as possible. In regards to the magnification, sometimes objects are considerably far away from the observer but higher the magnification, the more hand movements will translate into the view. Sea vessels already experience so much unwanted to-and-from motion and a binocular with instability issues will only make the situation worse. Similarly, larger objective lenses promise brighter images and since users do not have to carry devices and other gear on their shoulders, larger binoculars with higher magnification and bigger objectives are deemed suitable for marine purposes.
Generally, magnification of 7x is acceptable for use at sea because higher magnifications will reduce FOV and will have stability issues. Mariners usually prefer objective sizes of at least 50mm diameter, which will draw relatively more light and allow the observer to view distant islands and ships comfortably. Anything smaller than this would absorb less light and hence, the resulting images will be less bright. Getting a pair of binoculars that are both durable and features high-quality nitrogen purging and O-ring seals is essential or your binoculars might not experience much ocean time. Other important features include an integrated compass that is usually superimposed on the lenses enables the user to identify the trajectories of sea vessels, which are impossible to guess using conventional binocular models. Some high-end marine devices from manufacturers like STEINER and Nikon feature laser rangefinders (LRF), which are meant to know the distance of an object from the observer since it is difficult to estimate with the naked eye and a lack of stationary reference. Additionally, should your expensive binoculars go overboard, specialized floating straps will prevent them from sinking deep into the water. Due to their buoyant material, the straps will keep them afloat on the water surface, where they can be rescued easily without substantial damage.
The continued growth in demand for binoculars also stems from their gradual popularity in hiking, safari, and cycling trips. Although these fun activities do not completely rely on binoculars, they bring the excitement factor into your day by enabling you to look far ahead and observe the beautiful wildlife, waterfalls, distant lakes, and mountain peaks, especially when you are on the go.
Enthusiasts usually prefer binoculars that are at least between 7x30 and 8x40 capacity for uninterrupted viewing. Compact and lightweight binoculars that can be carried in backpacks and pockets are usually what hikers and cyclists prefer because larger binoculars set are difficult to carry and care for. Water and fog-proofing are a must because humidity and temperature can vary greatly outdoors and only an O-ring sealed device can fight against moisture contamination. A neck strap for carrying is also favored greatly among experienced users.
Theaters, such as the Sydney Opera house, where opera and other live shows take place are gigantic and have seating capacity for thousands of aficionados. Since everyone cannot enjoy amazing views while sitting right in front of the stage, guests who are at a distance, especially those on the balconies, either carry their hand-held theater binoculars or sometimes they come complimentary with premium seating by the organizers. These opera glasses enable visitors to enjoy close-up views of the performers since both the songs and performances are part of the opera experience.
The most common opera binoculars have magnification between 3x and 7x. The smaller objective lens ensures the binoculars remain compact and lightweight enough to be comfortably used for the duration of the performance. 3x-8x zoom is considered acceptable to be used in theaters since higher magnifications are not necessary in this case.
Stargazing is another interesting sport that is incomplete without a high-powered pair of binoculars. Most stars are just tiny dots in the sky and some cannot even be seen with the naked eye. While most people use telescopes to view them in the night sky, binoculars provide compactness, portability, wider field of view, and a more comfortable viewing experience due to the simultaneous involvement of both eyes. Since stars and other celestial bodies are the most distant objects in the universe, ultra high-powered binoculars are required to observe and identify them. In addition to extreme distances, most stars are quite dim, and to view such objects, optical devices with large objectives are preferred.
For astronomic objects such as the Moon or nearby star constellations, a magnification of 10x is more than enough, but if the goal to see the Orion Nebula or the rings of Jupiter, higher magnifications up to 20x are your best bet. The size of the objective lens plays an important role in the stargazing sport. Although well-lit objects such as the Moon, Jupiter, or the International Space Station are easily seen with conventional binocular sets, dull celestial bodies require larger objective lenses to capture more reflected light for images with extraordinary detail and contrast. Normally, astronomers are comfortable with objectives of 50mm or more in diameter.
Binoculars make excellent companions for uniformed officers and armedforces personnel. According to a study, at most 15% of all binoculars produced annually are sent to armed forces and law enforcement organizations around the world, especially coastguards and border control agencies. Most of these agents are part of covert missions and stealth is the key to getting successful in their respective assignments. Border control agents are regularly assigned with reconnaissance tasks that require precise observations of enemy movements along the border. Highly compact and robust binoculars provide a way for professionals to observe ungentlemanly conduct and grave crimes from a distance and enables them to take swift measures against the perpetrators before any serious damage is done.
Binoculars for military and coastguard operations usually start at 15x50 and go up to 20x100 models for bright images with accurate detailing. Since they are bigger than conventional models and can weigh up to 3kg, these binoculars come with tripod attachments for comfortable viewing and are generally not travel-friendly. National Police and State detectives, however, do not require high-powered binoculars and usually settle for 7x30 or 8x30 models.
Binoculars make excellent birthday and Christmas presents for children and spouses in families that go for annual camping and cycling trips. Children are especially inquisitive beings and binoculars can aid their curiosity by helping them observe objects that are far from their reach. Unlike mobile phones and games, kids can use binoculars to learn about birds, stars and other interesting objects which they normally study at school but do not have access to see them up close.
Entry-level binoculars that are generally 8x20 or 10x25 are suitable enough to be gifted to kids. Since children will not be using them for precise viewing or in a professional capacity, these binoculars need not be of superior quality or have nano-coated lenses, although a robust build will certainly come in handy because they will likely be dropped a lot.
Since their inception in the 17th century, binoculars have seen exponential growth in demand from nearly all parts of the world, especially just after the Second World War. The increase in demand has prompted many manufacturers to design specialized devices for specific purposes and scientific advancements have made it possible to have different binocular types for all kinds of uses. What was initially developed as a device for navigation and stargazing has turned into a tool for entertainment, leisure, sports, marine, vacation, and several other fun activities. Todaj it is impossible to perform hunting or birdwatching without a pair of binoculars.
Marine navigation binoculars generally feature magnifications from 7x to 8x and objective sizes from 30mm to 50mm. Since they lie in the premium category, some of these high-functioning binoculars contain built-in compass and an argon-purged body due to its capability of blocking a large amount of moisture from entering the housing. Binoculars for hunting and bird watching are generally mid-range devices that feature robust materials and compact sizes along with a smaller close focus and a wider field of view. Military binoculars, however, are large instruments with magnifications of up to 20x and objective sizes start from 50mm. These high-powered devices also boast armored chassis and enable users to view targeted objects from extreme distances without coming into someone’s radar.
Other activities that are incomplete without a set of binoculars include camping, hiking, plane-spotting, astronomy, opera performances, border control, and even activities like macro-photography and telephotography where enthusiasts place the sensor of their cameras to one of the eyepieces to take macro photographs of miniature objects and very distant objects respectively.
is an experienced author from the field of sports optics. He writes articles and reviews about binoculars, spotting scopes, rifle scopes, long range shooting and other topics for magazines like Lovec and Optics-Info.com blog. Currently, he is a member of Optics Trade team.