You can be a hunter or a bird watcher (an ornithologist,) or even military or marine personnel. You can do pretty little without good pair binoculars. But when you want to buy a pair for yourself, you know you can't hope to cross match the specifications of a bird watchers' needs with your, a soldier's, needs.

Considerations before Buying Binoculars
Fundamentally, since you are planning to buy binoculars, it goes imperative that they must match your needs. Binoculars are manufactured to suit specific needs of different professionals. Give a thought to the number of hours you use it on a day to day basis. Naval range finding binoculars are huge and weigh upto 10 tons. Secondly, buying binoculars is a very personal matter; how much weight you are comfortable with, what eyepiece suits you if you are bespectacled and so on.

Consider the Following Points First
Magnification and lens diameters are the fundamental parameters you must consider regardless of the type you require. Binocular of 7x35 means 7 times magnification of the objects than would be possible with naked eyes and the front lens has a diameter of 35 millimeters. Larger the diameter, larger is the field of view but magnification power decreases accordingly. Larger diameter also ensures clarity of pictures which otherwise would appear hazy. Just doubling the diameter quadruples the clarity by increased light gathering.

If your reason for buying binoculars is horse race watching or military surveillance, larger field of view suits better. Field of view signifies the area of vision specified in degrees. To understand the width of view from a distance of 1000 yards, multiply the specified degrees by 52.5.

The glare of lenses is reduced by special coating.
?Plain coating
?Full coating
?Multicoated
?Fully multicoated
Plain coating is very poor, so get yourself binoculars which are at least fully coated.

Check for rubber eyecups if you are bespectacled; next, if the lenses are fitted deep in, the field of view is curtailed even for persons without spectacles. As for focal length, a close range (15-18ft) would do better for birding. So, check whether you can focus your hand to confirm this point.

Zoom function helps adjust the power for birding and military purpose. For such binoculars the power is indicated in ranges like 10-50x50. This means the power ranges from 10 times to 50 which is the maximum.

Finally, what you can't forget are designs like Porro Prisms, Roof Prisms and pocket designs. The latter is handy owing to small size and weight but images will be darker. Porro prism designs provide larger exit pupils, quick & closer focus, wide field of view. But it's bulky. Roof prism design offers a lighter, water proofed binoculars but costs a hell.