Be sure to watch our helpful video: How to Choose a Binocular
Selecting the right pair of binoculars is a matter of picking the best combination of features for your particular needs, including magnification, bulk and weight, brightness, field of view, optical quality, and cost.
Understanding the Basics of Binoculars
Binocular sizes are expressed with two numbers: 7x35, 10x50, etc. The first number is the magnification (or power), the second is the aperture, or diameter of the objective (front) lenses in millimeters. For example, 7x35 binoculars provide 7x power magnification and have 35mm objective lenses. For a given magnification, larger objective lenses yield a brighter image in dim light, but also result in a bulkier, heavier pair of binoculars.
The higher the power, the "shakier" the image will be, because small hand movements get magnified. Therefore, we recommend binoculars of moderate 7x or 8x magnification unless you have a specific need for more power. Lower-power binoculars also usually offer a wider field of view, allowing you to take in more of a scene at one time.
To select the best binoculars for your own particular needs, let’s consider a few simple but vital questions and features:
1) What Will You Do With the Binoculars?
Hiking If you hike or travel a lot, you’ll want binoculars that are compact and lightweight, perhaps even weatherproof. An 8x24 or 10x25 would be a good choice, thanks to their small size, great portability, and good daytime performance.
Birding The most popular models for birdwatching are 8x40 and 8x42. They’re small and nimble, offer steady hand-held views, and have sufficient light grasp to provide bright, well-resolved images. If you plan to study birds at close range, look for binoculars with a near-focus distance of a few feet.
Astronomy For stargazing, light grasp is the most important factor. Choose binoculars with at least a 50mm aperture. A 7x50 model is easily hand-holdable and provides nice, wide-field views of starry swaths. The higher-power 10x50 is also popular, and in fact is preferable to the 7x50 where skyglow light-pollution is a problem. A tripod is recommended for a steady view through astronomy binoculars - your arms will thank you!
"Giant" astronomy binoculars of 70mm, 80mm, or 100mm aperture will reveal fainter deep-sky objects and more subtle detail. If you can afford the higher price (and a good tripod) and don’t mind the extra bulk, you’ll be rewarded nightly with incredible views.
Of course, other factors should play into your buying decision too, such as eye relief, optical coatings, and mechanical construction. If you need advice, give us a call!
2) Binocular Prisms: Porro vs. Roof
The prisms inside binoculars turn what would otherwise be an upside-down image right-side up. There are two main types of prism systems used in modern binoculars: porro prisms and roof prisms.
Each barrel of a porro-prism binocular contains two right-angle prisms. They are offset from each other, which requires that the objective lenses be spaced farther apart than the eyepieces. Thus, porro-prism binoculars are bulkier than their roof-prism counterparts. Optically, however, porro-prism binoculars usually perform better, because the prism design requires less strict tolerances. That makes them easier to manufacture, so they cost less. Also, porro prism binoculars yield a more stereoscopic, or three-dimensional, image.
The prisms in a roof-prism binocular overlap closely, allowing the objective lenses to line up directly with the eyepieces. This results in a more streamlined, compact, and often more lightweight binocular than equivalent porro-prism models. But roof-prism binoculars are also more difficult to manufacture, so they cost more. Roof prisms lose slightly more light to reflection than porro prisms - a disadvantage for astronomical use but not a concern for daytime terrestrial viewing. Well-made roof-prism binoculars can provide optical performance nearly equal to, but not better than, porro-prism binoculars.
Most optical prisms are made from either BK-7 (borosilicate) glass or BAK-4 (barium crown) glass. BAK-4 is the higher-quality glass and yields brighter images and better edge sharpness. It is also more expensive.
3) Field of View
The field of view is the size of the "window" you see through a binocular. The field has no effect on the size of the subject being viewed (that’s a function of the magnification). Surprisingly, the field of view is not determined by the binocular’s main (objective) lenses, but rather by the eyepiece and prism designs.
The width of the field is expressed either as an angular measure in degrees, or as a linear width measurement, in feet, of the viewing area at a distance of 1000 yards. You can convert from angular field to linear field by multiplying the angle in degrees by 52.5.
"Wide-angle" is an inexact term that simply indicates that a binocular field is wider than average. Generally, a binocular is considered wide-angle if its apparent field of view (angular field in degrees times magnification) is 60 or greater.
A wide-angle binocular is ideal for finding subjects quickly, and it can deliver spectacular panoramic views. A wide field is especially desirable for watching action sports or scanning to pick up motion at close range, such as in a wooded area. A narrower field of view is sufficient for longer-distance observation.
The Bottom Line
Deciding which pair of binoculars are best for you depends on your particular goals for using the binoculars. We recommend you take advantage of information and resources such as our website and catalog to help you make the most appropriate selection for you and your family. If you get stuck along the way, Orion is here to help you with any questions. Just send us an email at email@example.com, contact us via live chat, or give us a call Toll-Free at 800-676-1343 and we’ll help you find the right binoculars!
In closing, let’s re-visit some of the most important factors to consider:
1) What Will You Do With The Binoculars? - By far the most important factor to consider when choosing a binocular. For daytime outdoor use while hiking, a lightweight, compact and portable binocular is preferable. Birding enthusiasts will appreciate a slightly larger model with 36-42mm objective lenses as they provide brighter views with more detail visible than smaller binoculars. For nighttime use viewing starry skies, a larger astronomy binocular with at least 50mm diameter lenses is required for the best views.
2) Binocular Prisms: Porro vs. Roof - Once you’ve determined what you’ll be using binoculars for, you can consider what prism type to select for the best results. In general, porro prisms provide brighter views, but are often bulkier than roof prism binoculars. Roof prism binoculars are significantly more compact and portable than porro prism models, but they do not provide the same level of brightness, and are often more costly.
3) Field of View - A pair of binoculars with a wide field of view lets you scan vast areas with magnified vision. If you wish to view large areas such as sporting events, or scenic landscapes, a binocular with relatively low magnification and a wider field of view is recommended. However, if you wish to really zoom in on wildlife or starry skies, a higher-magnification binocular with a more narrow field of view may be preferable.
Don’t forget the most important factor of all - to enjoy your new binoculars and have FUN!