Binoculars Buying Guide |
Birding is one of the most demanding uses for binoculars you will find. Birders demand a level of detail that virtually no other hobby or situation requires and need optics that cover a wide range of situations. Because of that, there are some very important things to determine before buying binoculars. Below, we list many of the specifications to look for when deciding which binoculars are right for you. Or if you are in a hurry, skip the explanations and go directly to the quick reference chart at the bottom of the page.
First Things First:
It is usually best to determine what you want the binoculars to accomplish before going shopping since they can vary greatly in size, weight, and function. A few things to consider:
The Shape of Things:
Binoculars come in two basic shapes or styles: Roof-prism and porro-prism. Roof-prism binoculars are typically smaller and have a "straight-barrel" light path. Porro-prisms are the style most people see when they think of binoculars. There are very few differences between them when comparing image quality, but roof-prism designs are generally smaller and often more expensive due to a more complicated manufacturing process. 
By The Numbers:
Other than the overall size and shape, the first thing most people look for are "the numbers." They define the strength and light-gathering ability of a pair of binoculars. The first number (to the left of the "x") stands for the magnification power of the optics and tells you how many times larger or closer an image will appear than if using the naked eye. The second number (to the right of the "x") is the size of the front lenses (usually measured in millimeters) and determines how bright an image will appear.
Magnification:
It's tempting to buy the highest magnification possible, but that's not always the best idea. High magnification can be less desirable because it tends to make hand tremors more noticeable (unless you use a tripod), results in a smaller FOV, and amplifies earth processes such as heat being reflected (seen as wavy lines). Higher magnification may also result in images that are not as clear and bright. Lastly, higher magnification makes it more difficult to initially find objects and to track moving objects. For birding, 7x or 8x is typically recommended. 
Objective Lens Size:
This is the size of the front lens and is important because it affects the amount of light allowed into the binoculars. In most cases, the larger the front objective, the clearer and brighter distant images will appear, but also the heavier the optics. If you can foresee using your binoculars at dawn, dusk or any other time when there is little light, you will want to get a larger objective size. To give you an idea of how much impact this number can have, 35mm objectives will let in about three times more light than 20mm objectives based on pi(r)². More light usually results in a brighter, clearer image when all other factors (such as coatings) are equal. This is why most birders don't recommend buying compact binoculars and instead suggest something like 35mm or 42mm objectives.
Prisms:
The quality of glass used in prisms and how finely it is ground can affect the sharpness of images. The two more common types are BK7 and BAK4. Generally, BAK4 is more expensive, but considered better than BK7 for several reasons. One such reason is that BAK4 gives a nice round exit pupil while BK7 can produce distortion around the edge of the exit pupil as seen below. 
Coatings:
Coatings help reduce glare and improve contrast, among other things. If you hold the large front objectives towards you and notice a funny color on the lenses, those are the coatings. While there are several different levels of coatings (as discussed in the FAQ), the best optics carry the term "fully multi-coated."
Fixed or Zoom:
At first glance, zoom binoculars appear to be a great concept, but most birders should stick to fixed-power binoculars because zooms do have some drawbacks and limitations. It's true that zooms are wonderful because you can scan an area and when you find something you want to see, you can zoom in on the object and see more detail. However, zooms can result in darker, fuzzy and distorted images and a smaller than normal FOV. If you decide to buy zooms, be sure to try them out first (in a store or from a friend) to see how they perform.
Weight:
Weight can be a big concern depending on how you will be using your binoculars. If a tripod will be used, then the sky is the limit. However, if you plan to take your binoculars with you on the trail, you will probably want them to be as light as possible. However, heavier optics do have at least one advantage and that is that they resist movement (e.g. from wind) better than lighter optics. Specially designed straps can also make heavier optics more bearable by taking the weight off your neck and distributing it to your shoulders. Look for optics in the range of 15 to 35 ounces.
Price:
Prices for binoculars range from less than $20 of an inexpensive compact pair to more than $1,000 for a top-of-the-line pair. This number really depends on what you can afford. However, that old cliche about getting all that you pay for is very true of binoculars. As we recommend in the FAQ, beginners can start with optics in the $100 to $200 range and then trade up as they progress.
Conclusion:
The above are many of the most important factors to consider when purchasing binoculars. However, this list is not comprehensive because we wanted to keep it short and simple.
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