Binoculars come in all shapes, sizes, and price ranges, and can make any activity -- from bird-watching and sports to concerts and astronomy--more enjoyable. They allow us to see an actor's face up close as he portrays our favorite character, or to catch a glimpse of galaxies and nebulas millions of light years away.
In order to choose a pair of binoculars that are right for you, we have listed below information that is of a more general nature, but is important to know in choosing ANY binocular.
WHAT ELSE AFFECTS BRIGHTNESS?
EXIT PUPIL:If you divide the magnification of the binocular into the diameter of the lens, i.e. "35 divided by 7" or "50 divided by 10", you come up with the diameter in millimeters of the beam of light that is hitting your eye (35 divided by 7 = 5mm). The larger the number, the more light (or information) your eyes are receiving. Why is this important? Let's say you are looking for a pair of binoculars for bird-watching, you know that you typically are out at dawn or dusk doing your observations, and you find that many times, the birds you are observing are sitting in bushes, hidden in the shadows. Well, if you buy a small pair of binoculars, say a 10X25 compact, you will have an exit pupil of 2.5mm. The pupils of our eyes dilate anywhere from 2mm to 7mm, depending on the lighting conditions. The lower the light, the larger our pupils dilate (maximum dilation decreases as we get older, about 1mm for every 10-15 years beyond the age of 30). So, at age 40, under lower light conditions (not dark) your eyes would be dilated to about 4mm +/-. That means that your eyes would be receiving a lot less light through the 10x25's than they could if you had a pair of binoculars whose "eyes" were dilated closer to your own. So, if you are going to participate in activities that find you in lower light conditions, make sure to buy a pair of binoculars that will assist you in seeing better instead of hindering you. How about a pair of 7 x 50's, for instance? This gives you an exit pupil of 7.14mm... just about maximum for most people's eyes, no matter what your age. A pair with an exit pupil like this will bring as much light to your eye as possible... a high priority in poor light.
WHAT IF I WEAR GLASSES?
If you wear glasses, eye relief is especially important to you. The term "eye relief" means the distance between the binoculars and your eyes to see the entire field of view or achieve a good image. This number is also represented in millimeters, and generally ranges from 5-20mm. Rubber eye cups help to place your eyes at the correct distance for comfortable viewing. If you wear glasses when using your binoculars, either because you are correcting for astigmatism or because it is your preference, eye relief becomes critical. The longer the eye relief, the easier it will be to get a good image with your glasses on without dealing with the "tunnel vision" effect, since they are forcing your eyes away from the eyepieces. The best way to use your binoculars with glasses is to roll the eye cups back and place your glasses right on the padded surface that is revealed. Try for at least ten millimeters of eye relief for the best results... fifteen is better!
Tips: How to Choose Binoculars (Part One)
1. Bushnell Outdoor Sports 20X50 Binoculars Telescope
2. Bushnell Outdoor Sports 20X40 Binoculars Telescope