1. Make sure the power (or magnification) is at least 7-power. The power is the first number given in the numerical notation that describes binoculars. For example, a "7 X 35" pair of "glasses" will make objects appear as if they are seven times as close as they actually are. Seven-power binoculars are about the minimum needed to see birds well. Binoculars 10-power or stronger can be difficult for some birders to hold steady.
2. Make sure that the second number ("35" for a "7 X 35" pair of glasses) is at least five times as large as the power (e.g., "7 X 35," "8 X 40," etc.). This second number describes the diameter, in millimeters, of the large lens that faces the object of interest - the "objective" lens. The larger this lens is, the greater the amount of light the binoculars gather and thus the easier it will be to see characteristics in dim light or on a dull-colored bird.
3. Are the binoculars too heavy for you to carry and use for at least two hours straight? Don't end up with a hunchback because your binoculars act like a yoke.
4. Can you flex the barrels of the binoculars fairly easily? To test to see if they are too flexible, spread the barrels out as far as possible and then hold onto only one of the barrels. Does the free barrel slip or fall from the spread position? It shouldn't.
5. When held a foot away, do the large objective lenses reflect a bluish or purplish tinge? If they do, the lenses are color-coated. This coating reduces internal glare in the binoculars and increases the amount of light that actually comes to your eyes. Check lenses to make sure the coatings are free of any blotches or scrapes.
6. Can you bring the barrels of the binoculars close enough together so that the image you see merges into a single, clear image within a single, perfect circle? If the image isn't singular or clear, the binoculars may be out of alignment or the eyepieces may not come close enough together to accommodate your eyes. These two problems may lead to eye strain and severe headaches.
7. Do you wear prescription eyeglasses? If you do, your binoculars should have rubber eye cups that fold back. This allows you to put your eyeglasses up closer to the eyepieces of your binoculars and gives you a much larger field of view.
8. Do the binoculars produce a clear image of an object only 20 feet away? Some binoculars do not focus on objects this close, so you may miss the sparrow or warbler that skulks in a nearby bush.
9. Look at a sign with large lettering. Do the letters close to the edge of the field of view appear as precise and well-formed as the letters in the center of the field of view? Image distortion towards the edge of binoculars is common in bad binoculars - like looking through a fish-eye lens. Look for a pair that has minimal distortion
10. When you focus on a license plate or small sign two blocks away, are the letters and numbers clear? If they're not, choose a different pair!
One thing about binoculars is that you don't always have to have the best specs for bird watching. Any binoculars are better than none at all. The thing to remember is that you need to have something to magnify the birds you will be looking for. If you are serious about bird watching, take heed of the tips for buying binoculars given above. They will be well worth the money!
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