Using Your Binoculars

Adjusting Your Binoculars to Your Eyes: A new pair of binoculars can open your eyes to the beauty of the world all around you. But no two people’s eyes are exactly the same. When you take your binoculars out of the box, you need to adjust a few settings so they will work perfectly for your eyes.

Eye cups: If you don’t wear eyeglasses, extend the eye cups. Eye cups are designed to block out peripheral light and to hold the ocular lens of the binoculars at the precise distance from your eye to give you the largest image and widest field of view possible with those binoculars. If you do wear glasses, fold down or push the eye cups in. Your glasses are already holding the binoculars away from your eyes. With the eye cups pushed in, your eyeglasses will hold the binoculars away from your eyes at about the proper eye relief distance. If your eye cups are adjustable, you may want to try the different settings to see at which one your view is largest.

Interocular distance: To get a clear view without blackouts or dark shadows, the two barrels of your binoculars must be set to match the distance between your eyes. Pull the binoculars out and push them in until you’ve found the width that allows you to see most clearly through both eyes.

Setting the diopter adjustment: Almost all binoculars have a “diopter adjustment” which allows you to set the two sides of your binoculars to match the differences between your eyes. It is typically on the right side, and usually is marked with a zero between a plus and a minus sign. Find it and make sure it’s set at zero before you start this adjustment.

Find something that isn’t close to your binoculars’ nearest focusing range, but isn’t too far away, to focus on—a sign or poster with words and/or numbers works well. If you’re in a large room, something on the opposite wall should be perfect. Then follow these steps while standing in the same position:

• 1. Place the lens cap or the palm of your right hand over the right objective lens (or the left hand over the left lens if that’s the side with the diopter adjustment) and focus on the object using the central focus. Make the focus as crisp as you can. Try to do this without closing your other eye.
• 2. Switch your hand or lens cap to cover the other objective lens, and now make the same object as crisp as you can using the diopter adjustment.
• 3. Switch your hand or lens cap again to double check how good the focus is—if adjustments are necessary, use the central focus.
• 4. Then switch your hand or lens cap one last time, and fine tune the diopter adjustment.
• 5. Now look through both lenses, and make sure the object is well-focused. Focus on something closer, and something farther away, using the central focus, to make sure the binoculars are set right. Then notice exactly where the diopter adjustment is set. This is where it should stay whenever you use your binoculars. (If you sometimes wear different glasses or contact lenses, your diopter adjustment setting may be different in those situations.) You should always use the center focus now.

If you share your binoculars with someone else who requires a different diopter setting, you have four choices. 1) Change it every time you pass the binoculars back and forth. 2) Set it halfway between your best settings as a compromise. 3) Leave it set for one person, making the other person’s eyes do a little extra work. 4) Buy another pair of binoculars so you can each have your own.

Every now and then, it’s a good idea to check that your diopter adjustment is set where it belongs. And once in a while you should retest the diopter setting in case your vision has changed.

Getting You and Your Binoculars Field Ready

If your binoculars have a one-piece rain guard to protect the optical lenses from rain, follow the manufacturer’s directions for getting them affixed to the strap. Separate lens caps can be very inconvenient in the field. If your binoculars didn’t come with an easy-to-use rain guard, you can make your own with a piece of chamois or oil cloth by cutting it in an oval a couple of inches wider and longer than your binoculars, and cutting a hole in an appropriate spot for dangling it from the strap. A rain guard is good not only in inclement weather or when the wind sends lake or sea spray your way—it also affords excellent protection while you eat your lunch.

If you wear your binoculars on a harness rather than a strap, follow the manufacturer’s directions for sizing it and attaching it to the binoculars. If you wear a neck strap, adjust the length so it is long enough to get the binoculars easily over your head but short enough that the binoculars rest on your chest rather than your stomach. The longer the strap, the more the binoculars will bounce and the more likely they are to bonk into things whenever you lean over.

If you’re new at using binoculars, it’s easiest to practice looking at one or two things guaranteed not to fly away before you try them out on birds. Look at a picture or sign or other object, and keep your eyes on it as you pull up your binoculars. Is the object right in the middle of your binoculars? If so, that’s beginners luck! Usually it will be somewhat above or below your field of view, and you will have to pull the binoculars slightly up or down. Try this on several familiar objects as you get comfortable with working with your binoculars as a team.

If you wear eyeglasses, get used to keeping them on while you use your binoculars. The two or three seconds (or more!) that it takes for you to put your eyeglasses into a pocket and to refind the bird and get your binoculars up may be longer than the bird feels like staying in one spot. You’ll see more birds if you learn to use your binoculars with your eyeglasses. Make sure the eye cups are all the way down on your binoculars to make your view through eyeglasses crisper and larger. If your binoculars have a lower eye relief than is optimal for your eyeglasses, your view will be smaller. Next time you get eyeglasses, you might consider frames that hold the lenses closer to your eyes. When I got a new pair of eyeglasses that were more close-fitting, I felt like a got a new pair of binoculars, too—that’s how noticeable was the improvement.

Now it’s time to go birding!
Practice on a robin, pigeon, or other backyard bird first. When you spot it, keep your eyes on it as you pull up the binoculars, and quickly compensate if there was a shift in your field of view, as you did indoors. Soon spotting and getting birds quickly and easily into your binocular view will be second nature.

Remember when looking at birds in the sky to be mindful of where the sun is so you don’t accidentally scan right into it.

~ Laura Erickson