Please note that I do not define all the terms in this page. I have included a Binocular Terminology link.
Choosing the right binocular for my purpose
To choose the right binocular for your purpose you have to clearly identify your purpose. From this you will have a list of criteria to apply to your search.
Binocular sprecification lists are hugely confusing if you don't know what you want.
Features to consider when choosing Binoculars
Magnification or Power, how large does the image have to be. Larger image will show more detail but any movement of your arms while holding the binoculars will be multiplied.
Magnification (the first number describing the binoculars) can be as low as 3 or 4 for small opera glasses or tiny pocket binoculars and they are often used inside. An example is the: Bushnell Spectator Sport 4x 30mm Extra Wide Field of View Binoculars.
Because of the simple optics, with no prisms and no focusing, they tend to be less expensive.
Nikon also has a 4X magnification compact binocular. It has both focusing and prism: Nikon Binoculars Yu 4X10D CF Wine Red
Another common use of 4x magnification is in spotting scopes on Guns.
Magnification of 6 to 8 are more common and often considered the most practical range. It offers the advantage of useful magnification without the disadvantages of high magnification such as shaky view, and reduced viewing angle. The majority of binoculars sold are in this range and a wide range of options are available.
Because of the moderate magnification, the binoculars can be hand held. Moderate shaking such as in a boat does not interfere too much, particularly if the binoculars have a wider field of view.
Higher magnification 10 upwards to 25 and more are specialized instruments. They are often found on Astronomy binoculars or on military or law enforcement equipment.There is a wide price range in this category. A resonable astronomy binocular can be as low as 100 or less dollars and the sky is the limit. Here is Celestron SkyMaster 25X100 ASTRO Binoculars with deluxe carrying case As with many astronomy binoculars, it has a large objective to collect as much ligh as possible. It is surprisingly inexpensive and makes a good entry level (and more) astronomy binocular.
In the more pricey range, the Steiner 20x80 Senator Binocular is a rugged high magnification large aperture binocular that is aimed at military type use but would work just as well for astronomy.
Some high magnification binoculars offer image stabilization, at a cost. An example is from Canon: Canon 18x50 Image Stabilization All-Weather Binoculars w/Case, Neck Strap & Batteries
Image Stabilization is available. It is a battery powered system and various system have been tried. Motion sensors adjust the optical path often by shifting the prisms which stabilizes the image. Canon has many different models such as the well reviewed: Canon 10x30 Image Stabilization II Binoculars
One of the advantages of using image stabilization is being able to use higher magnification and still not have to use a tripod. It is very intersting for boat owners. Since image stabilization is a feature offered in higher end binoculars, the optical components are usually quite good and this makes for brighter and sharper images than lower end instruments.
How bright does your viewed image need to be. If you are viewing at night or in low light then you need all the brightness you can get. This usually translates in large objectives 35 to 50 mm are practical sizes. If you view in sunlight, it is not much of an issue and you can use binoculars with a smaller objective saving size and weight.
Quality of the lens, coatings and prism also has an influence on the amount of light which is gathered and transmitted so a smaller objective with better quality components might bring in as much light as a lower end binocular.
What exit pupil is best. To take full advantage of the light gathered by your binoculars, you want to match the exit pupil of the binocular to the size of the human pupil in the chosen light. The pupil will dilate to 5-7 mm in low light and contract to 3 or so in bright light. More details on exit pupil in my Binocular Terminology page
Age of user has a bearing on how well the eye adapts to low and bright light and on the useful exit window. The older you get the smaller the range of dilation-contraction.
What angle of view do you need. Wider angle of view allow you to spot and follow a moving object such as birds or sports action, much more easily than a narrower angle. The higher the magnification the smaller the angle of view.
Water proof is nice if you use your binoculars on water or in bad weather. There are several manufacturer: waterproof binoculars
Weight is an important issue. If you need to carry your binoculars for long periods you will want a more compact binocular. Many of the newer binocular are manufactured with roof type prisms which allow for straighter optical path. This allows the binocular to be smaller. The older porro prisms make for a larger binocular but with better depth of field 3-d view.
Because roof prisms are harder to manufacture in binoculars of similar quality, the roof system will be more expensive than porro prisms. In lower quality binoculars roof prisms sometimes lose lights or cause light flashes because of the more complicated manufacturing and more complex visual path. There are 2 extra bends in roof prisms.
The size of the objective has an impact on the weight of the binocular as well. Here is a list of compact binoculars compact binoculars
How close can you focus. Will you be looking at near things like butterflies, or will most of your observations be of far objects. If you're looking at birds you want to see quite close. If you are looking over water from a boat, you don't need a close focus. Here is a binocular by Zeiss that has a 5 foot focus.ZEISS 524205-9904 Terra 8x42 ED Binoculars, Lost Camo There are several binoculars in the Terra series.
Is 3-d / depth of view important. Separating the objectives increases the 3-d effect while making them close flattens the image. The down side is that the larger the binoculars, the more heavy they become.
Eye relief (the distance between your eye and the occular lens) matters if you need to wear glasses. Too little eye relief is more tiresome as well and can cause condensation from your eye, in cold weather.
Tough and rugged for children. Another point to consider is the minimum separation distance of the eyepieces. If it is wider than the eyes of the child the binoculars will not be able to be properly used because the eyes will not line up to the binoculars. Here is a selection of children's binocular childrens binoculars As usual you get what you pay for. If you get too cheap a pair they will not work well and will not last. Better to spend a bit more and have a useful pair of binocular for several years.
Price has to suit your budget. Luckily, some very nice binoculars are available quite well priced.
Bragging right. Do you want the absolute best latest gadget and best optics? try out the Carl Zeiss Optical 10x42 Victory HT Binocular Many people consider them the best in the world.
email me if you find mistakes, I'll fix them and we'll all benefit: Christine