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Optics Primer

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What do the numbers mean?

Example: Swarovski EL 10 x 42 (read as 10 by 42)

The first number is the magnification or how many times larger an object will appear when viewed through the binoculars. Our binoculars range from 6x to 10x magnification with 8x being the most popular model we sell. While higher magnifications allow you to see more detail, they require a more steady hand to avoid a blurry image. Also, as magnification increases, the field of view (the widest view you can see from left to right) narrows.

The second number is the size of the objective lens (the lens which is furthest from your eye). It is the measurement in millimeters of the width of the lens. The size of the objective lens determines how much light enters the binoculars which, in turn, effects how bright the resulting images can be. The size of this lens is the major factor in determining how large the binoculars will be and what they will weigh.

 

What determines the quality of the image?
There are three factors that most affect the quality of the image.

  • The quality of the optical glass that is used determines how bright, sharp and colorful the resulting image will be. Glass used in the objective lenses of top quality optics will contain fluorite crystals to offer a clear, bright image. That type of glass is called Extra Low Dispersion (ED), though some manufacturers use the letters HD,HT, XD or FL to describe this type of fluorite lens.

  • Anti-reflective coatings eliminate internal reflections and light scattering, reduce glare and produce sharper images with more detail. The type of coatings and number of coatings applied to the lenses determines how brilliant and crisp the image appears.

  • The size of the exit pupil or the beam of light that exits each eyepiece of the binocular and enters the user’s eyes determines how bright the image will appear, especially in low light conditions (when comparing optics of similar glass and coating quality). The exit pupil is measured in millimeters, and is calculated by dividing the objective lens by the magnification. The larger the exit pupil the more light you see. Our best-selling binocular size, 8 x 42, has a 5.25mm exit pupil (42 divided by 8 equals a 5.25 exit pupil).

What is the best binocular to buy?
Many factors will shape your decision. Our prices range from $30 to nearly $3,000. In addition to price range, you’ll need to consider where you will be using the binoculars (most all of ours are waterproof), the typical distance you’ll be viewing (across the yard to your backyard feeder or at a lake focusing on a far shoreline), how much weight you want to carry (are you a backpacker?) and most importantly, what feels comfortable and easy to use in your own hands.

How do I find out what binoculars are the best for me?
Come in to the Nature Store and try out some of our quality optics. Our experienced and helpful store staff and volunteers are happy to help you select the pair of binoculars that is just right for your own particular needs. We’ll be happy to discuss warranties with you and show you how to adjust binoculars for the best viewing with or without eyeglasses.

Spotting Scopes
The Nature Store also carries a selection a spotting scopes for birders. Currently we carry sighting scopes by Swarovski, Kowa, Leupold, Vortex and Carl Zeiss. Stop by to have a look. Hope to see you soon!

 
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