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What defines good binoculars focusing system for bird watching?

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While the most common use of binoculars is in the hunting field, in reality, the most demanding binocular users are the bird watching enthusiasts. This is not surprising, since birds are some of the fastest and unpredictable species of animals. Their intriguing nature and beauty are the reason millions of bird watchers set out to observe migrating and native birds every year in specific seasons all over the world.

Birds frequently move impressively fast and have a camouflaged appearance, and even a slight hint of human presence scares them away. Watching them from a suitable distance is, therefore, necessary for anyone who is willing to observe the rarest of birds. An expert birder always uses a pair of binoculars with the highest optical performance in order to locate and observe them properly. The focusing mechanisms made for binoculars for bird watching have to enable fast changes and rapid adjustments. For this reason, we call such focusing mechanism fast focusing.

Most will think that a bigger magnification is the key to successful bird watching, however, this is not the case. While a good magnification is a must, too high of a magnification is usually not advised, because the user will have to compromise on the field of view. The movement of birds between tree branches is so sudden that a higher magnification combined with a comparatively small field of view will make it quite difficult for the user to keep up with their movements.

In addition to the field of view, the focusing mechanism of binoculars needs to be quick and effective. Consider a scenario in which you are out in the fields observing the migratory birds when you come across a Turquoise-Browed Motmot sitting calmly on a tree. You are mesmerized by its beautiful colors and while you are having the time of your life, it suddenly flies to a nearby tree which is a little farther from where you are. You catch up with the bird by moving a little closer to it, but now your set of binoculars cannot focus on the bird. This is when the effectiveness of the focus mechanism comes into play.

Since a pair of binoculars can focus at one distance at a time, its focus needs to be calibrated every time you want to observe a different object at a new distance. A quick focusing mechanism will allow you to resume your viewing in a swift manner, whereas a time-consuming focus system will ruin your experience.



Birds are one of the most intriguing species among all life forms. Apart from some, most birds move extremely fast and in an unpredictable manner, especially in the presence of an unknown individual. Thanks to their efficient wings, birds can fly from a very close range to a distant tree in a matter of seconds, so it is quite possible to lose their sight. As mentioned earlier, this problem can be resolved with the help of a fast focusing mechanism.

Most bird watchers are interested in watching rare species of birds, which usually migrate between the North and South regions. The reason for bird-migration is mostly because of access to abundant nesting locations and burgeoning insect populations in areas with good weather conditions. This is when avid birders have a good chance to spot a variety of rare birds.

Since the weather is pleasant, most people combine their annual camping trips with bird watching. This gives a chance to the whole family, especially children, to enjoy the beauty of unusual birds. Although most families carry separate sets of binoculars for each member, it is not uncommon for multiple family members to share their binos. For this purpose, these binoculars must be user-friendly to accommodate multiple users with varying viewing skills and levels of patience.

Bird watching trips usually take a considerable amount of time, therefore, birders are advised to choose a pair of binoculars with optimum objective lens size, since it determines the weight and size of the binoculars. While a large-sized bino will draw in more light and produce a sharper image of birds, pausing after every few minutes to rest your hands will take out the fun from the trip. Objective sizes of 42mm or less are generally considered the standard for bird watching.

The Ultimate Compact Binoculars Buying Guide

Modern binoculars are available with either of the following two focusing systems:


Nowadays, the Central Focus or CF mechanism is universally used in binoculars to adjust the focus, especially in bird watching binoculars, due to their centralized focus adjustment. A pair of binoculars with central focus comes with a central knob, which when turned in either direction controls the movement of ocular lenses in both barrels simultaneously to adjust the focus until the intended object becomes focused. Like animals, birds have an excellent camouflaged appearance which helps them to remain safe from large predators. To spot such birds, expert bird watchers understand the role of the focus mechanism in binoculars.

As discussed above, birds move extremely fast in comparison to other animals. To observe them without interruption, you will need to have a set of binoculars whose focus can be adjusted swiftly. There is usually not enough time for adjusting the focus, therefore, the central knob provides an easy and quick way to adjust the focus while you continue to hold the binoculars with one hand and track the birds. Optics manufacturers have begun to put special emphasis on this central knob due to the role it plays in bird watching. In addition to its size, the location of the knob in the binoculars is also crucial for a seamless focus adjustment.

Fast-focusing mechanisms have a central wheel that usually does only one turn or even less from one extreme focusing position to another. That means that even a slight movement changes the focus considerably. This works very well for bird watchers but is not suitable for hunters that are usually observing slow-moving animals and need a slow and finely adjustable focusing mechanism.

Binoculars from premium binoculars, such as Zeiss, Swarovski, and Leica have positioned the focus knob in alignment with the usual location of the index fingers. This helps the user to comfortably adjust the focus while still using their binoculars. Also, these binoculars have large focusing knobs with appropriate knurling, which makes it easy to rotate it in either direction, especially while wearing gloves which is rare. The central focus system in binoculars is immensely popular among birders due to its simplicity and quick adjustment. CF binoculars are also favored by families on their annual camping trips since they can be shared among multiple users without having to calibrate every time a different family member wants to use them.

While they are liked by many, CF binoculars usually have poor waterproofness capability compared to individual focus binoculars. This is due to the interconnection of both barrels, which makes it a daunting task for optics manufacturers to achieve an ideal water and fog proof capability.

Zeiss Conquest HD 8x42


The individual focus or IF system allows birders to adjust the focus of each barrel of binoculars separately irrespective of each other. To achieve this, binoculars with individual focus mechanisms have diopter rings on top of each barrel near the eyepiece instead of one knob in the center. The rings can be turned in either direction to adjust the focus of barrels one at a time.

Although they offer precise control of the focus mechanism, the IF mechanism is not really practical for bird watching. The reason is that birds are known to move quickly from branch to branch and it is not uncommon for birds to fly to a distant location from a nearby tree in a matter of seconds. This behavior makes it difficult to follow the birds, even with a central focus mechanism. With individual focus, there is not enough time for bird watchers to pause and adjust the focus every time a bird changes its location. Additionally, these binoculars cannot be shared among multiple family members during camping trips since they are adjusted for one user at a time. Calibrating them each time a different person needs to use them can be cumbersome for most people and it can ruin a fun-filled day. Therefore, we do not recommend such binoculars for bird watching.

However, these binoculars have certain advantages over CF binos. For instance, people who wear prescription eyeglasses due to a difference in acuity can use these binoculars without their eyeglasses. This can be done by incorporating the difference in acuity into the binoculars while adjusting the focus. Another advantage is better fog-proof and water-proof capabilities. Since the barrels are not inter-connected, there is a lesser chance of Nitrogen gas leakage in case these binoculars fall on a hard surface. Lastly, IF binoculars perform better in low-light conditions because the focus needs to be adjusted only once.


Unlike most animals, birds have razor-sharp eyes which helps them to spot insects, predators, and other birds in their surroundings effectively. Even if they are sitting calmly on a tree branch, their eyes are still doing most of the work. This is why they fly from branch to branch unpredictably. Take the example of the Swallow. It could be sitting just 5 meters away from you on a wall and while you take out your binoculars, it flies to a tree branch 50 meters away from you. Therefore, the focus mechanism must be quick enough to incorporate fast changes to the view, otherwise, observing birds would be impossible.

Binoculars today come either with a central focus or individual focus system. Both of these systems have their pros and cons, but the latter is usually considered unusable for bird watching due to its time-taking focus mechanism. CF binoculars are at an advantage here, since they provide a central knob for focus adjustment that can be used to adjust focus for both barrels simultaneously. This way, birders can easily track and catch up with birds.

We at Optics Trade always recommend central focus binoculars that are capable of quick focus adjustments, perfect for our bird watching customers.



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