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How to Test Binoculars

Birder with Binocular

These tips are from the instructions we gave to our team of testers this summer when we were reviewing mid-priced binoculars for Bird Watcher's Digest. (See the review in the November, 2007, issue of the magazine).

These are points to consider when you're trying to decide whether a binocular is the one for you.

Getting ready

1. Set the eyecups for yourself.
Some eyecups push/pull in and out. Some twist in and out. A few fold down or up.

  • If you wear glasses, put the eyecups in the short, or down position.
  • If you do not wear glasses, put the eyecups in the long, or out position.

2. Set the distance between the eyepieces for your own eyes.

Flex or extend the central hinge between the two barrels until you see one circle while looking through the binocular.

Evaluating the binocular

1. Focus Knob
This is your most important control. You don't have to be a binocular expert to judge it. Is it well located? Does it turn smoothly? Too stiff or too loose? Is there slack or uneven resistance? Can you focus from close to far quickly?

2. Fit & Feel
Everybody's size, shape, and hands are unique. Feel how the binoculars fit your hand and in general how nice they are to hold. Points to consider:

  • Texture. Does it feel good to your skin?
  • Weight. Is it too heavy for you to want to carry?
  • Balance. Easy to hold?
  • Shape. Do your hands just fall in the right place? Strap lugs don't dig into your hands?
  • Eyecups. Fast and easy to adjust? Shaped right for your eyes and glasses? Not too hard?
  • Hinge. Does it work smoothly? Not too stiff? Not too loose to hold its position?

3. Image Quality

  • Brightness. Clear and full of light, rather than greyer or darker?
  • Sharpness. Ability to resolve fine detail.
  • Contrast. Can you see fine gradations of darkness, like a brown creeper on a tree trunk?
  • Edge to edge sharpness. Can you see details clearly at the edges of the image?
  • Freedom from color aberrations. True colors—not like looking through colored glass.
  • Freedom from fringing. You should not see red and green echoes along sharp edges, such as when viewing a black power line against a light sky.

4. Glasses Friendly

If you wear glasses, check the binocular's glasses friendliness. First put the eyecups in the up position, and look through the binocular without your glasses. Notice how wide the field of view is.

Then put your glasses on, put the eyecups in the down position, and look again.

If the field of view is just as wide it was without your glasses, the binocular has good eye relief and rates a good score for glasses friendliness. If the eyecups are hard to manipulate or if they don't maintain their position, that is not so good.

Copyright 2007 Michael and Diane Porter

Other optics articles of interest:

Birding Optics

10 Myths of Birding Optics

Birding Binoculars and How They Work

The Binocular Advisor

Binocular Picks for Every Price Range

 

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