Adjustment and Alignment
Before you start to use a new pair of binoculars, you should check them for alignment and adjust the focus for your eyes.
All quality binoculars provide independent focus adjustment of each eyepiece. The actual procedure varies from one pair or manufacturer to the next. In general the process is something like this.
The center focus knob is used to focus in on specific, distant object. It is the prime focus for the binoculars and one of the eyepieces.
The other eyepiece will have a further adjustment to compensate for focus differences between your eyes. Check the user manual for your binoculars to determine which eyepiece has the additional adjustment and where it is located. The adjustment is often right on the eyepiece, but can be located above or below the central focus knob.
To set the focus adjustment:
1. Select a distance object on which to focus
2. Focus on the object using the center focus knob.
3. Close the eye that is viewing through the eyepiece with the fine adjustment, and refocus on the object as needed.
4. Close the other eye and look through the eyepiece with the fine adjustment. Make any focus adjustments needed with the fine adjustment for that eyepiece.
That's it! Your binoculars are now calibrated. Some binoculars have a scale on the eyepiece with the fine adjustment. This can be used as a quick reference for checking the focus.
Binoculars that are not properly aligned can make focusing difficult and result in a headache after long use. You should check the binoculars for alignment before purchase, if possible, or immediately after receiving them. You can check the alignment with the following steps.
1. Adjust the binocular focus using the steps above.
2. Focus on a distant , horizontal straight line. The top of a home or building works fine.
3. Holding the binoculars as steady as possible (use a tripod if possible), position the binoculars about 8 in. in front of your eyes.
4. Alternately look through each barrel by closing one eye at a time.
The height of the straight line (rooftop or building) should appear at the same position when looking through both barrels of the binocular. If the lines are at different levels, the binoculars are out of alignment.
It can take a little practice to make this technique work, so give it a couple of chances before reaching a conclusion.
Repairing a pair of binoculars that is out of alignment is a bit tricky. If such a situation exists, the binoculars should be returned to the manufacture for repair.