What is a Compact Binocular?

Like any binocular, it is an optical instrument that allows the user to view objects in the distance clearly. They consist of two small telescopes situated side-by-side, each having a pair of lenses that will bring the objects closer. The difference is that a compact binocular is a smaller design than the ‘full-sized’ optic and their slim design makes them more portable and convenient to use. They are even small enough to fit in a purse or a large pocket. Since they are small in size, this means that the front lenses are smaller, usually having the objective lens of 26mm or less. Some compacts do have an objective lens of 28mm, but you will find that these models are larger in size, which could make it tough to fit in a purse. Compacts are a favorite of those with an on the go lifestyle and like having their instrument around with them on their activities. The lightweight of the instrument makes it easy to take with you on your excursions, such as hiking, cycling, bird watching or even just on a walk outdoors! Of course, like anything else there are advantages and disadvantages to having a compact binocular. Understanding the use of your instrument will help you further in deciding if the compact if the perfect instrument for you or not.

Porro and Roof Prism

The compact comes in two different types of prisms; the Porro prism and the Roof prism. The difference in type affects the shape of the optic, which will in turn have different feels in handling quality. Lets begin with the Roof prism.

Roof Prism

This prism system is popular amongst many due to its slim design making it actually “compact” in size. In this system the eyepieces and front lenses are overlapping each other in a straight line giving it the sleeker streamlined shape. When looking into this design, make sure the instrument you use is a Phase-Corrected (PC) roof prism, because it will allow you to have better image quality and contrast. The Phase-Corrected roof prism will be more expensive then a regular roof prism, but it is worth investing in if you need performance and want to keep up optically with porro prism compacts. Of course, when looking into body design of the optic, you have some options on how the roof prism compact folds. The most popular system of this kind is the double hinge design. What makes this design special is that it allows each binocular barrel to fold inwards against a third section on the body. This makes the instrument take the minimum amount of space needed allowing it to fit smoothly anywhere you would want to carry it, even the pockets of your jacket! However, the double hinge design has its downside. It can be slow to open and align the barrels together, which can take away some viewing opportunities, especially when you want to get in the action fast. If you don’t mind your instrument not being able to fold and taking up a little more space, the single hinge design would be a better recommendation since it will be quicker and easier to open allowing you to get right in the action fast! Not to mention it is less prone to having the barrels get out of position when worn around your next as opposed to the double hinged design.

Porro Prism

Unlike the Roof prism, the Porro prism does not have the eyepieces and front lenses in a straight line. It actually has the front lenses sit out wider than the eyepieces; making this prism system less compact than the roof prism. This is why there is a variation of porro prism design and the one used in small binoculars is known as the “Reverse Porro Prism”. By its name you can conclude that it is opposite of the porro prism; this means is that the eyepieces sit out wider than the front lenses. Because of how the system is set up it is very easy to distinguish the porro prism. When compared to the roof prism, it is much bigger and chunkier in size making it harder to use but it has many advantages that may allow you to overlook its size. Efficiency wise, the porro prism is optically more capable than a roof prism. Also, with a porro prism you will get more quality for what you pay opposed to the quality you will get with the money you spend on a roof prism.

Advantages to Compact Binoculars

What makes this instrument so very popular is the fact that it is “compact” in size making it portable and lightweight that you’d want to take it everywhere you go! Imagine being on a hiking excursion and seeing something in the far distance but not be able to see if because you do not have your instrument with you! A lot of people invest in the most expensive optic, but what use is it to have when it’s put away at home or in the car? The compact instrument allows you to observe the greatest objects in any circumstances. Many bird watchers love this instrument because birds, much like other animals appear unexpectedly and in unexpected places, making the compact perfect for the occasion! You don’t want to miss those special moments because your instrument is still in the car. Many owners of full-sized binoculars have a compact instrument for activities such as bird watching, hiking, hunting or even photography!

Due to the fact that the size of the compact is small and they are made of smaller lenses, and in addition are less expensive to produce to high optical standards than the larger lenses. This usually makes the premium compact optic almost always better than the larger premium counterpart. Especially when it is compared in terms of edge sharpness and freedom from barrel distortion, flaring and coma.

Another advantage is that a compact is relatively cheaper in price than its full-sized counterpart. Imagine you can buy an excellent compact for half the price of the full-sized instrument! This can play well for you if you have a smaller price range in mind, but still want a quality pair!

Disadvantages to Compact Binoculars

Just as it has its advantages, it also has its disadvantages. Due to the fact that it is compact in size, the objective lens is also small in size therefore not giving the same resolution capability that you would receive with the larger siblings. This will limit you in terms of details you will be able to see and the sharpness of the image will not appear as crisp compared to the larger model. This is because optically speaking; the size of the lens is correlated to the ability to separate fine detail. When comparing a compact model with different models and sizes, you have to keep in mind that lens quality is just as important as lens size when it comes down to performance. This can significantly enhance the quality of instrument you have. For example if you have a high grade, premium quality compact binocular with polished lenses, it can without a doubt outperform a cheap full sized binocular.

Another disadvantage to the compact is that because of its compact size, the smaller objective lenses will produce smaller exit pupils (the light that exits the eye piece and enters the eye), which can cause eye fatigue especially when using the instrument for long periods of time. With a lot of these instruments, if the centering is a little bit off, it will produce eyestrain. This is why it is important to set the interpupillary adjustment (this is the width between the barrels to fit your eyes) properly and carefully, because just as the way that if it is not centered will cause eyestrain, so will it if the binocular is too wide or not wide enough. Of course, with time you will get the hang of adjusting it properly and this problem will not be an issue anymore. It is suggested that if you will be using the instrument for long periods of time, the full sized optic would be a better choice for the situation. Compacts are better suited for casual lookouts during the day, not for long observing sessions.

The fact that the compact is ‘compact’ in size is great when in terms of easy handling, but it does interfere with the image brightness you receive. Much like the low-resolution issue, because the objective lenses are small the brightness of the image is significantly lower. Smaller front lenses don’t take as much light as the larger lenses, but this shouldn’t be as big of an issue as people make it. When you compare two instruments, a premium compact with a larger sibling, in the field during the day, the compact can hold its own in terms of brightness. The issue comes into play when you want to use it in very low light conditions, otherwise the compact will serve you well during the day.

Getting the right instrument is sometimes hard to do, but understand what you need it for and how often you will use it will help you pave the way there. The main reason behind getting a compact is the fact that it can fit anywhere and it is light to hold, which is perfect in situations such as hiking or going for a nature walk. Sometimes size and weight work against you when you want to hold the optic steady. It is often recommended when buying a full sized instrument (and not wanting to use a tripod) that the magnification is 10x or less, because of the image steadiness that you can get. In comparison the compact 10x is even harder to hold steady than the full sized optic because it is so light in weight. Of course, getting a smaller magnification will make it much easier to steady than a higher magnification. This is why the 8x compact is mostly used, it is easier to steady and the wider field of view makes it easy to do many activities, such as bird watching. For your first compact an 8x would serve you well all around in terms of quality and ease.

With a compact, don’t get distracted by a bigger number of magnification. The smaller the magnification the better compact you will have. A 10x sounds exciting, but don’t let the number fool you! If this is your first binocular, 10x is not recommended, whether it’s in compact or full sized unless you are planning on using a tripod with it. Even if you are planning to use a tripod, you need to make sure that the instrument you have is compatible for the use of tripods. But having to get a tripod to be able to use your compact efficiently will be spoiling the entire point of having a compact in the first place!

Looking at Some Features

Eye Relief

This refers to the distance between your eyes and the binoculars while the whole field of view is still visible. Longer focal length of an eyepiece, gives greater eye relief. This is ideal for people who wear eyeglasses and manufacturers have made binoculars with twist-up, pop-up or soft rubber fold-down eyecups, which go down. This is an important specification for eyeglasses wearers to look out for when buying their instrument. It is recommend that eyeglass wearers look for an eye relief of 11mm or more, although a 14mm or 15mm will give a better eye relief to see enough of the field of view while wearing your glasses, but this can vary from person to person and the thickness of the eye glass can also play a part. For those who have different vision in each eye, there is a diopter adjustment that will give the viewer a better experience. It is a ring situated behind the eyepiece lens that allows you to focus each lens individually. Also, there is an inter-pupillary distance number, which refers to the distance between the eyes of a person. This obviously differs from person to person and can be fixed by opening or closing the hinge to either bring the eyepieces closer together or further apart. Typically the inter-pupillary distance ranges from 60mm to 72mm.

Field of View

Is the measurement of area that can be seen through your binoculars. It is the width of the area, usually in feet, visible at 1000 yards or meters. The field of view can be measured by two things; the magnification and the eyepiece design. First thing to know is, when the magnification power is higher the field of view is lower. Therefore, when looking at an object at 1000 yards a 10x will show you more details of the object than an 8x, but you will not see it in a wide view. The wide-angle design also is a determinant of the field of view. This matters if using the instrument for astronomy, a wide field of view will be more desirable to see the sky at a fuller view, making the experience more enjoyable. Most binoculars have focus knobs and what this will give you is the “close focus”. This being the closest distance your instrument will focus on an object. This feature is one to look out for if you are using your instrument for bird watching. Because a compact is so small, you won’t find many with “wide angles” although you will get plenty of field of view, just not as much as wide angled designs. Again, depending on the activity you will be using it for you can decide whether this is something that is important to have.

Waterproof and Armoring

This would be a good idea if you are planning to use your instrument in the cold, wet or extreme weathers. It can be a useful feature to have since it also has the proper protection against dust, dirt and fog! You don’t want to be admiring nature with a foggy or messy instrument. Armoring is not necessary but it is a practical investment to keep your instrument protected from any nicks or scratches that could occur. You don’t want a silly misfortune to ruin your entire lens and not to mention experience! Also, armoring can make the instrument more comfortable to hold in hot or cold weather and can help you have a better grip on the optic.

Focus

Focus knobs will be a feature you will find on most binoculars, and properly designer ones will allow you to focus with simply one finger. A compact with a larger focusing knob will serve you better than tiny focusing knobs because it will allow you to focus properly and with ease, especially in cold or extreme weathers and while wearing gloves. The ones you find with tiny focusing knobs are better suited for indoor activities, such as going to the theater or an opera.