How to Use Binoculars
By James Davis , Metro Park Naturalist
You will only get the most out of your binoculars ("binos") if you know how to adjust them properly. Many people do not know how to use the Adjustable Eyepiece (diopter) and never really see as well as they could with their binoculars.
Here are easy, step by step instructions for making the FOUR adjustments needed to get the best out of your "binos."
Note: This is why sharing binoculars is not usually practical. Each person needs to have a pair of binoculars adjusted for his or her eyes.
Modern binoculars have either soft rubber eyecups or twist up/down eyecups on the eyepieces that can fold down or rotate down to adjust for eyeglasses. If you use binos with your glasses on, rotate down eyecups so the end of the eyepiece is as flat as possible. Put the flat eyepiece right on your glass's lens when using the binos. If you are not wearing glasses, leave the eyecups extended. A few types of binoculars have eyecups that screw in to get flat for glasses.
The two halves of the binos are joined together in the center with a hinge. This is so you can move them in and out until they are the right distance apart for your eyes. While looking through the binos, move them in and out until you have one big, clear, circular field of view. If you get dark patches or crescents in the center or on the sides, they are too close together. You should never see two circles. Keep fiddling with them until you get the best field of view and don't be afraid to keep adjusting them throughout the day.
3. CENTRAL FOCUS
Hold the binoculars in both hands and reach to the center with a big finger or two and turn the wheel in the center. This is the Central Focus . Turn the central focus back and forth every time you look at something new to get the sharpest, clearest image you can. However, your eyes are probably not the same and you need to make one more adjustment to see as well as you can with your binoculars.
4. ADJUSTABLE EYEPIECE
" Left eye - Central Focus then Right eye - Adjustable Eyepiece "
This is the most confusing thing about using binoculars. Almost no one ever explains it on nature and birding walks and it is often poorly explained in the instructions that come with binoculars (yes, there were some). It is even explained wrong in some bird watching books.
When you use the Central Focus , you focus the two sides of the binoculars at the same time. BUT, your eyes are probably not identical. So you need to adjust your binoculars so each side is in focus for each eye at the same time. You do this by using the Adjustable Eyepiece through diopter .
FIND IT -- The Adjustable Eyepiece is the one that TURNS and it will have a simple scale on the underside of the eyepiece with a " -, 0, + " and another mark next to the scale on the bino frame. Binos differ, but almost all have the Adjustable Eyepiece on the right. Find your Adjustable Eyepiece and turn it. Find the scale on the underside and set it at "0" or "in the middle".
Here is the easiest way to make this adjustment, step by step.
(For an Adjustable Eyepiece on the right.)
• Pick something sharp and clear to look at, a medium distance away, like a sign.
• Make the other adjustments and focus on the sign with the Central Focus as best as you can.
• Close your right eye and use the Central Focus to get the left eye's image as sharp as possible. You are only looking through the left side of your binos.
• Now, close your left eye and open your right eye. Don't touch the Central Focus . You are now looking through only the right side of your binos.
• Here's the tricky move. Turn the Adjustable Eyepiece back and forth with your right hand until you get the sharpest image you can in your right eye . See? You are matching your right eye to the left eye.
• Open your left eye and the object should be in sharp focus in both eyes. To check, focus on something else using both eyes with the Central Focus , then alternate looking with one eye and then the other. The image in both eyes should look the same and be in sharp focus. If not, try turning the Adjustable Eyepiece a tiny bit back and forth to see if you can get it sharper. Sometimes you just have to fiddle a bit with the Central Focus and the Adjustable Eyepiece until you get them just right.
• When you have the Adjustable Eyepiece in the right position, look at the scale and remember that setting. This is your basic setting for those binos, always start with that. Many people find that their eyes change from time to time so don't be afraid to keep fiddling with it to get the best image you can.
Remember: Left eye - Central Focus then Right eye - Adjustable Eyepiece
Zen-Ray is very grateful that the renowned Portland Metro Naturlist and avid birder James Davis agrees to share his excellent procedure for using and adjusting binoculars for bird watching on zen-ray.com