How to Calibrate Binoculars

Calibrating your binoculars allows you to customize them to make up for the difference between your eyes. This will focus your binoculars for an optimal viewing experience.


  1. Image titled Calibrate Binoculars Step 1
    Stand 30ft (approximately 9.14 metres) away from a sign with clear lettering (street signs are ideal). Turn the center focusing wheel counterclockwise as far as possible.
  2. Image titled Calibrate Binoculars Step 2
    Locate the diopter adjustment ring, a focusing ring located on one of the eyepieces (usually the right). It is usually marked with the following: - 0 +. Turn this ring as far counterclockwise as possible.
  3. Image titled Calibrate Binoculars Step 3
    Point the binoculars at the sign. Look through your binoculars with both eyes open. With your hand, cover the end of the barrel that has the diopter ring. Turn the central focusing wheel until the lettering on the sign comes into sharp focus.
  4. Image titled Calibrate Binoculars Step 4
    Cover the end of the opposite barrel. Turn the diopter ring until the lettering comes into sharp focus. Your binoculars are now calibrated to your eyes.
  5. 5
    Looking through both eyes, check it is comfortable. If one of your eyes is straining to focus closer than the other, move the binoculars a few inches away from your eyes so they see your surroundings, as well as your target in the central spot. This helps your eyes relax. Repeat the left-right-both focussing steps above with the binoculars held away.


  • You may want to tape the diopter ring in place when you are done calibrating to prevent it from shifting.
  • If the barrels of the binoculars cannot come close together enough to suit your eyes (in other words, if an annoying gray shadow keeps on appearing), then the binoculars are too big for you. You should be able to 'bend' them around the central axis to bring the tubes closer together or further apart as needed.
  • When the eyepieces are the correct distance apart, moving them (or your head) left and right will make both eyes go dark at the same time.
  • If you see a double image, try moving them a few inches away from your face, while still looking at something. If the image stays double, or you lose one image, your bins need repair. Gentle tapping might pop a prism back into place. Your eyes might point in different directions, which is tiring.
  • If you see two overlapping circular fields-of-view (but not a double-image), don't worry. Think of it as extra-wide-angle. Makes finding and following things easier.
  • Or note the position so you can reset them if you share them.


  • Don't look into the sun with your binoculars.
  • Don't drop your binoculars.

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Categories: Birdwatching | Wildlife